Latest / Okay, But... Birds / Okay, but how do birds stay warm?

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Okay, but how do birds stay warm? · Okay, But... Birds

• 0:00
  A
• 0:00
  lot
• 0:00
  of
• 0:00
  our
• 0:00
  big
• 0:01
  owls,
• 0:01
  like
• 0:01
  snowy
• 0:02
  owls,
• 0:02
  you
• 0:02
  know,
• 0:03
  you
• 0:03
  hear
• 0:03
  that
• 0:03
  they
• 0:04
  can
• 0:04
  survive
• 0:04
  temperatures
• 0:05
  down
• 0:05
  to
• 0:05
  negative
• 0:05
  80
• 0:06
  degrees
• 0:06
  Fahrenheit,
• 0:07
  which
• 0:07
  is
• 0:08
  cold.
• 0:09
  That's
• 0:09
  crazy.
• 0:10
  Very
• 0:10
  cold.
• 0:10
  Really?
• 0:11
  That's
• 0:12
  what
• 0:12
  I
• 0:12
  read.
• 0:12
  I
• 0:12
  don't
• 0:13
  know
• 0:13
  who's
• 0:13
  out
• 0:13
  there
• 0:13
  measuring
• 0:14
  the
• 0:14
  temperature
• 0:14
  when
• 0:14
  it's
• 0:15
  negative
• 0:15
  80.
• 0:15
  And,
• 0:16
  like,
• 0:16
  bird
• 0:16
  watching,
• 0:17
  they're
• 0:17
  dead.
• 0:42
  Have
• 0:42
  you
• 0:43
  ever
• 0:43
  been
• 0:43
  really
• 0:44
  cold?
• 0:44
  Like,
• 0:45
  I
• 0:45
  can't
• 0:45
  feel
• 0:45
  my
• 0:46
  feet.
• 0:46
  Cold.
• 0:46
  My
• 0:47
  face
• 0:47
  feels
• 0:47
  like
• 0:47
  it's
• 0:48
  freezing
• 0:48
  cold.
• 0:49
  I'm
• 0:49
  never
• 0:49
  going
• 0:49
  to
• 0:49
  feel
• 0:50
  warm
• 0:50
  again.
• 0:50
  Cold.
• 0:51
  When
• 0:51
  I
• 0:51
  was
• 0:52
  first
• 0:52
  learning
• 0:52
  how
• 0:52
  to
• 0:52
  ice
• 0:52
  skate,
• 0:53
  that
• 0:53
  was
• 0:53
  a
• 0:53
  weekly
• 0:53
  experience
• 0:54
  for
• 0:54
  me,
• 0:54
  especially
• 0:55
  my
• 0:55
  feet.
• 0:56
  By
• 0:56
  the
• 0:56
  end
• 0:56
  of
• 0:56
  a
• 0:56
  skating
• 0:57
  lesson,
• 0:57
  my
• 0:57
  toes
• 0:57
  were
• 0:58
  little
• 0:58
  popsicles,
• 0:58
  And
• 0:58
  I
• 0:59
  remember
• 0:59
  my
• 0:59
  dad
• 0:59
  sometimes
• 1:00
  helping
• 1:00
  to
• 1:00
  warm
• 1:00
  up
• 1:00
  my
• 1:01
  feet
• 1:01
  with
• 1:01
  his
• 1:02
  what
• 1:02
  then
• 1:02
  seemed
• 1:02
  to
• 1:03
  me
• 1:03
  giant
• 1:03
  hands
• 1:04
  after
• 1:04
  I
• 1:04
  got
• 1:04
  off
• 1:04
  the
• 1:04
  ice.
• 1:05
  And
• 1:05
  though
• 1:05
  I
• 1:06
  loved
• 1:06
  being
• 1:06
  on
• 1:06
  the
• 1:06
  ice,
• 1:07
  the
• 1:07
  cold
• 1:07
  feet
• 1:07
  that
• 1:07
  went
• 1:07
  along
• 1:08
  with
• 1:08
  the
• 1:08
  early
• 1:08
  stages
• 1:09
  of
• 1:09
  learning
• 1:09
  how
• 1:09
  to
• 1:09
  ice
• 1:09
  skate
• 1:10
  were
• 1:10
  uncomfortable
• 1:11
  and
• 1:11
  something
• 1:11
  I
• 1:12
  dreaded.
• 1:12
  Cold
• 1:13
  feet
• 1:13
  was
• 1:13
  also
• 1:13
  the
• 1:14
  most
• 1:14
  common
• 1:14
  complaint
• 1:15
  from
• 1:15
  the
• 1:15
  kids
• 1:15
  I
• 1:15
  eventually
• 1:16
  taught
• 1:16
  to
• 1:16
  skate,
• 1:16
  which
• 1:17
  is
• 1:17
  why
• 1:17
  there's
• 1:17
  one
• 1:18
  winter
• 1:18
  scene
• 1:18
  that
• 1:18
  always
• 1:19
  reminds
• 1:19
  me
• 1:19
  of
• 1:19
  my
• 1:19
  frozen
• 1:20
  skating
• 1:20
  toes.
• 1:21
  A
• 1:21
  duck
• 1:22
  standing
• 1:23
  on
• 1:23
  the
• 1:23
  ice,
• 1:24
  not
• 1:24
  pacing,
• 1:24
  not
• 1:25
  hopping,
• 1:25
  not
• 1:26
  doing
• 1:26
  the
• 1:26
  human
• 1:26
  thing
• 1:26
  where
• 1:27
  you
• 1:27
  pretend
• 1:27
  you're
• 1:27
  fine
• 1:27
  while
• 1:28
  your
• 1:28
  body
• 1:28
  is
• 1:28
  quite
• 1:29
  quietly
• 1:29
  calling
• 1:29
  for
• 1:29
  help,
• 1:30
  just
• 1:30
  standing
• 1:31
  on
• 1:31
  the
• 1:31
  ice.
• 1:31
  Calm,
• 1:32
  like
• 1:32
  frozen
• 1:33
  ponds
• 1:33
  are
• 1:33
  a
• 1:33
  totally
• 1:34
  normal
• 1:34
  place
• 1:34
  to
• 1:35
  hang
• 1:35
  out
• 1:35
  barefoot.
• 1:36
  And
• 1:36
  every
• 1:37
  time
• 1:37
  I
• 1:37
  see
• 1:37
  it,
• 1:37
  even
• 1:38
  though
• 1:38
  I
• 1:38
  know
• 1:38
  what's
• 1:38
  going
• 1:38
  on
• 1:39
  now,
• 1:39
  my
• 1:39
  brain
• 1:40
  does
• 1:40
  the
• 1:40
  same
• 1:40
  thing.
• 1:41
  Brr.
• 1:42
  Because
• 1:42
  if
• 1:42
  you
• 1:43
  and
• 1:43
  I
• 1:43
  tried
• 1:43
  that,
• 1:43
  we'd
• 1:44
  last
• 1:44
  about
• 1:44
  12
• 1:44
  seconds
• 1:45
  before
• 1:45
  we
• 1:45
  started
• 1:45
  panicking.
• 1:46
  Ducks
• 1:47
  and
• 1:47
  geese
• 1:47
  on
• 1:47
  ice.
• 1:48
  Chickadees
• 1:48
  turning
• 1:48
  into
• 1:49
  little
• 1:49
  puffballs,
• 1:49
  tiny
• 1:50
  birds
• 1:50
  that
• 1:50
  weigh
• 1:50
  less
• 1:51
  than
• 1:51
  a
• 1:51
  few
• 1:51
  nickels,
• 1:51
  making
• 1:52
  it
• 1:52
  through
• 1:52
  nights
• 1:52
  where
• 1:52
  the
• 1:53
  air
• 1:53
  itself
• 1:53
  feels
• 1:54
  sharp.
• 1:55
  So
• 1:55
  today's
• 1:56
  episode
• 1:56
  is
• 1:56
  about
• 1:56
  that
• 1:57
  mystery.
• 1:57
  Okay,
• 1:58
  but
• 1:58
  how
• 1:58
  do
• 1:58
  birds
• 1:58
  stay
• 1:59
  warm?
• 1:59
  And
• 1:59
  I
• 1:59
  don't
• 2:00
  mean
• 2:00
  the
• 2:00
  vague
• 2:00
  they
• 2:00
  have
• 2:01
  feathers
• 2:01
  answer.
• 2:02
  I
• 2:02
  mean,
• 2:02
  what
• 2:02
  are
• 2:03
  the
• 2:03
  actual
• 2:03
  moves?
• 2:04
  What's
• 2:04
  happening
• 2:04
  inside
• 2:04
  their
• 2:05
  bodies?
• 2:05
  What
• 2:05
  choices
• 2:06
  are
• 2:06
  they
• 2:06
  making?
• 2:06
  And
• 2:07
  what
• 2:07
  does
• 2:07
  it
• 2:07
  cost
• 2:07
  to
• 2:08
  stay
• 2:08
  alive
• 2:08
  when
• 2:08
  you're
• 2:09
  a
• 2:09
  small
• 2:09
  animal
• 2:09
  with
• 2:09
  a
• 2:09
  high
• 2:10
  body
• 2:10
  temperature
• 2:10
  living
• 2:11
  in
• 2:11
  a
• 2:11
  world
• 2:11
  that's
• 2:12
  trying
• 2:12
  to
• 2:12
  freeze
• 2:12
  you?
• 2:13
  To
• 2:13
  help
• 2:13
  us
• 2:13
  answer
• 2:13
  that
• 2:14
  question,
• 2:14
  I'll
• 2:14
  be
• 2:14
  joined
• 2:14
  by
• 2:14
  Dr.
• 2:15
  Maria
• 2:15
  Steger,
• 2:15
  an
• 2:16
  assistant
• 2:16
  professor
• 2:16
  at
• 2:16
  the
• 2:17
  University
• 2:17
  of
• 2:17
  Massachusetts
• 2:18
  Amherst
• 2:18
  who
• 2:19
  studies
• 2:19
  how
• 2:19
  birds
• 2:19
  cope
• 2:20
  with
• 2:20
  cold,
• 2:21
  how
• 2:21
  they
• 2:21
  generate
• 2:21
  heat,
• 2:22
  how
• 2:22
  they
• 2:22
  keep
• 2:22
  it,
• 2:22
  and
• 2:23
  how
• 2:23
  flexible
• 2:23
  they
• 2:23
  can
• 2:24
  be
• 2:24
  when
• 2:24
  winter
• 2:24
  throws
• 2:24
  them
• 2:25
  curveballs?
• 2:25
  And
• 2:26
  here's
• 2:26
  what
• 2:26
  I
• 2:26
  can
• 2:26
  promise
• 2:27
  you.
• 2:27
  The
• 2:27
  answers
• 2:27
  are
• 2:28
  amazing.
• 2:29
  We'll
• 2:29
  start
• 2:29
  with
• 2:29
  the
• 2:29
  duck
• 2:30
  feet
• 2:30
  question,
• 2:30
  because
• 2:30
  it's
• 2:31
  the
• 2:31
  One
• 2:31
  on
• 2:31
  everyone's
• 2:32
  mind.
• 2:32
  But
• 2:32
  the
• 2:32
  story
• 2:33
  gets
• 2:33
  weird
• 2:33
  fast.
• 2:34
  Like,
• 2:34
  what
• 2:35
  if
• 2:35
  the
• 2:35
  whole
• 2:35
  point
• 2:35
  isn't
• 2:35
  keeping
• 2:36
  the
• 2:36
  feet
• 2:36
  warm?
• 2:37
  What
• 2:37
  if
• 2:37
  the
• 2:37
  feet
• 2:37
  are
• 2:38
  doing
• 2:38
  something
• 2:38
  totally
• 2:38
  different
• 2:39
  than
• 2:39
  you
• 2:39
  assume?
• 2:40
  Then
• 2:40
  we'll
• 2:40
  go
• 2:40
  bigger.
• 2:41
  Birds
• 2:41
  don't
• 2:41
  just
• 2:41
  get
• 2:42
  through
• 2:42
  the
• 2:42
  cold.
• 2:42
  Some
• 2:43
  of
• 2:43
  them
• 2:43
  turn
• 2:43
  their
• 2:43
  bodies
• 2:43
  into
• 2:44
  heat
• 2:44
  machines.
• 2:44
  Some
• 2:45
  of
• 2:45
  them
• 2:45
  change
• 2:45
  how
• 2:45
  they
• 2:46
  insulate
• 2:46
  themselves.
• 2:47
  Some
• 2:47
  of
• 2:47
  them
• 2:47
  change
• 2:48
  how
• 2:48
  they
• 2:48
  behave.
• 2:49
  And
• 2:49
  some
• 2:49
  of
• 2:49
  them
• 2:49
  do
• 2:49
  something
• 2:50
  that
• 2:50
  sounds
• 2:50
  like
• 2:50
  science
• 2:50
  fiction
• 2:51
  the
• 2:51
  first
• 2:51
  time
• 2:51
  you
• 2:51
  hear
• 2:52
  it.
• 2:52
  They
• 2:52
  can
• 2:52
  temporarily
• 2:53
  run
• 2:53
  their
• 2:53
  bodies
• 2:53
  differently
• 2:54
  at
• 2:54
  night
• 2:54
  to
• 2:54
  save
• 2:55
  energy.
• 2:55
  We'll
• 2:56
  also
• 2:56
  talk
• 2:56
  about
• 2:56
  the
• 2:56
  parts
• 2:57
  of
• 2:57
  birds
• 2:57
  you
• 2:57
  don't
• 2:57
  think
• 2:57
  of
• 2:58
  as
• 2:58
  temperature
• 2:58
  tools.
• 2:59
  And
• 2:59
  then
• 3:00
  we
• 3:00
  zoom
• 3:00
  out
• 3:00
  to
• 3:00
  the
• 3:00
  modern
• 3:01
  world.
• 3:01
  Because
• 3:01
  winter
• 3:01
  isn't
• 3:02
  just
• 3:02
  cold,
• 3:02
  it's
• 3:03
  unpredictable.
• 3:04
  We're
• 3:04
  seeing
• 3:04
  weird
• 3:04
  extremes
• 3:05
  like
• 3:05
  polar
• 3:05
  vortex
• 3:06
  events
• 3:06
  hitting
• 3:07
  places
• 3:07
  and
• 3:07
  seasons
• 3:07
  that
• 3:07
  aren't
• 3:08
  prepared
• 3:08
  for
• 3:08
  them,
• 3:09
  and
• 3:09
  that
• 3:09
  can
• 3:09
  be
• 3:09
  catastrophic
• 3:10
  for
• 3:10
  the
• 3:10
  wrong
• 3:10
  bird
• 3:11
  at
• 3:11
  the
• 3:11
  wrong
• 3:11
  time.
• 3:12
  Especially
• 3:12
  birds
• 3:13
  that
• 3:13
  rely
• 3:13
  on
• 3:13
  food
• 3:13
  sources
• 3:14
  that
• 3:14
  simply
• 3:15
  disappear
• 3:15
  when
• 3:15
  it
• 3:15
  freezes.
• 3:16
  So
• 3:16
  today
• 3:17
  we're
• 3:17
  going
• 3:17
  to
• 3:17
  explore
• 3:17
  the
• 3:18
  physics,
• 3:18
  the
• 3:18
  biology,
• 3:19
  the
• 3:19
  behavior,
• 3:19
  and
• 3:19
  the
• 3:19
  survival
• 3:20
  math
• 3:20
  that
• 3:20
  lets
• 3:20
  birds
• 3:21
  stay
• 3:21
  warm
• 3:21
  and
• 3:22
  why
• 3:22
  some
• 3:22
  birds
• 3:22
  are
• 3:22
  better
• 3:23
  built
• 3:23
  for
• 3:23
  weird
• 3:23
  winters
• 3:24
  than
• 3:24
  others.
• 3:24
  Because
• 3:25
  the
• 3:25
  next
• 3:25
  time
• 3:25
  you
• 3:25
  see
• 3:26
  a
• 3:26
  duck
• 3:26
  standing
• 3:26
  on
• 3:26
  ice,
• 3:27
  I
• 3:27
  want
• 3:27
  you
• 3:27
  to
• 3:27
  have
• 3:27
  a
• 3:27
  new
• 3:28
  thought.
• 3:28
  Not
• 3:28
  just,
• 3:28
  how
• 3:28
  are
• 3:29
  you
• 3:29
  doing
• 3:29
  that?
• 3:29
  But,
• 3:30
  oh,
• 3:30
  you've
• 3:31
  evolved
• 3:31
  to
• 3:31
  do
• 3:31
  this.
• 3:32
  After
• 3:32
  the
• 3:32
  break,
• 3:33
  Dr.
• 3:33
  Maria
• 3:33
  Steger
• 3:34
  helps
• 3:34
  us
• 3:34
  unpack
• 3:34
  how
• 3:34
  birds
• 3:35
  survive
• 3:35
  when
• 3:35
  everything
• 3:35
  around
• 3:36
  them
• 3:36
  is
• 3:36
  frozen.
• 3:37
  Stick
• 3:37
  around.
• 3:43
  Welcome
• 3:43
  back,
• 3:44
  everyone.
• 3:44
  Thanks
• 3:44
  so
• 3:44
  much
• 3:45
  for
• 3:45
  joining
• 3:45
  us
• 3:45
  today.
• 3:45
  I'm
• 3:46
  really
• 3:46
  excited
• 3:46
  to
• 3:46
  chat
• 3:46
  with
• 3:46
  you,
• 3:47
  Maria.
• 3:47
  Thanks
• 3:47
  for
• 3:48
  having
• 3:48
  me,
• 3:48
  Scott.
• 3:49
  Yeah.
• 3:49
  So
• 3:49
  I
• 3:49
  thought
• 3:49
  we
• 3:49
  could
• 3:50
  start
• 3:50
  off
• 3:50
  by,
• 3:50
  I
• 3:50
  think,
• 3:50
  a
• 3:51
  question
• 3:51
  a
• 3:51
  lot
• 3:51
  of
• 3:51
  people
• 3:51
  have
• 3:52
  wondered,
• 3:52
  which
• 3:52
  is
• 3:52
  this.
• 3:53
  You
• 3:53
  see
• 3:54
  ducks
• 3:54
  and
• 3:54
  geese
• 3:54
  standing
• 3:55
  on
• 3:55
  the
• 3:55
  ice.
• 3:55
  You
• 3:56
  and
• 3:56
  I
• 3:56
  would
• 3:56
  struggle
• 3:57
  with
• 3:57
  that.
• 3:57
  It
• 3:57
  would
• 3:57
  be
• 3:57
  painful,
• 3:58
  and
• 3:58
  we
• 3:58
  would
• 3:58
  lose
• 3:58
  a
• 3:58
  lot
• 3:58
  of
• 3:59
  body
• 3:59
  heat.
• 3:59
  So
• 3:59
  what's
• 4:00
  the
• 4:00
  deal
• 4:00
  with
• 4:00
  waterfowl
• 4:01
  and
• 4:01
  their
• 4:01
  legs?
• 4:02
  Yeah,
• 4:03
  that's
• 4:03
  a
• 4:03
  great
• 4:03
  question.
• 4:04
  So
• 4:05
  birds
• 4:05
  in
• 4:05
  general,
• 4:06
  not
• 4:06
  just
• 4:06
  waterfowl,
• 4:07
  have
• 4:08
  what's
• 4:08
  known
• 4:08
  as
• 4:09
  countercurrent
• 4:09
  heat
• 4:10
  exchange.
• 4:11
  And
• 4:11
  so
• 4:12
  this
• 4:12
  is
• 4:12
  a
• 4:12
  principle
• 4:13
  from
• 4:13
  physics
• 4:14
  where
• 4:14
  if
• 4:14
  there
• 4:15
  are
• 4:15
  two
• 4:15
  fluids
• 4:16
  that
• 4:16
  are
• 4:16
  moving
• 4:16
  past
• 4:17
  each
• 4:17
  other
• 4:17
  in
• 4:17
  opposite
• 4:18
  directions,
• 4:19
  heat
• 4:19
  can
• 4:19
  be
• 4:19
  transferred
• 4:20
  from
• 4:20
  one
• 4:20
  to
• 4:21
  the
• 4:21
  other.
• 4:21
  And
• 4:22
  so
• 4:22
  what
• 4:22
  birds
• 4:22
  do
• 4:23
  is
• 4:23
  they
• 4:23
  have
• 4:24
  blood
• 4:24
  vessels
• 4:24
  that
• 4:24
  are
• 4:25
  really
• 4:25
  close
• 4:25
  to
• 4:25
  each
• 4:26
  other,
• 4:26
  and
• 4:26
  blood
• 4:26
  is
• 4:27
  traveling
• 4:27
  in
• 4:27
  opposite
• 4:28
  directions.
• 4:28
  So
• 4:28
  they
• 4:28
  have
• 4:29
  arteries
• 4:29
  carrying
• 4:29
  blood
• 4:30
  from
• 4:30
  their
• 4:30
  heart
• 4:31
  down
• 4:31
  to
• 4:31
  their
• 4:31
  feet.
• 4:32
  That
• 4:32
  blood
• 4:32
  is
• 4:32
  really
• 4:33
  warm.
• 4:33
  And
• 4:33
  then
• 4:33
  they
• 4:34
  have
• 4:34
  veins
• 4:34
  that
• 4:34
  are
• 4:35
  carrying
• 4:35
  blood
• 4:35
  from
• 4:36
  their
• 4:36
  feet
• 4:36
  back
• 4:36
  towards
• 4:37
  the
• 4:37
  heart,
• 4:37
  and
• 4:37
  that
• 4:38
  blood
• 4:38
  is
• 4:38
  much
• 4:38
  cooler.
• 4:39
  And
• 4:39
  by
• 4:39
  putting
• 4:40
  those
• 4:40
  two
• 4:40
  blood
• 4:41
  vessels
• 4:41
  really
• 4:41
  close
• 4:42
  to
• 4:42
  one
• 4:42
  another,
• 4:43
  they
• 4:43
  can
• 4:43
  transfer
• 4:44
  heat
• 4:44
  from
• 4:45
  the
• 4:45
  artery
• 4:46
  to
• 4:46
  the
• 4:46
  vein.
• 4:47
  And
• 4:47
  so
• 4:47
  by
• 4:47
  the
• 4:47
  time
• 4:48
  the
• 4:48
  blood
• 4:48
  gets
• 4:48
  to
• 4:48
  the
• 4:49
  foot,
• 4:49
  there's
• 4:49
  a
• 4:49
  lot
• 4:50
  less
• 4:50
  heat
• 4:50
  that
• 4:51
  is
• 4:51
  going
• 4:51
  to
• 4:51
  the
• 4:51
  foot.
• 4:52
  And
• 4:52
  in
• 4:52
  this
• 4:53
  way,
• 4:53
  they
• 4:53
  can
• 4:53
  actually
• 4:53
  conserve
• 4:54
  heat.
• 4:56
  And
• 4:56
  so
• 4:56
  in
• 4:56
  a
• 4:57
  way,
• 4:57
  their
• 4:57
  foot
• 4:57
  ends
• 4:57
  up
• 4:58
  being
• 4:58
  much
• 4:58
  colder.
• 4:59
  But
• 5:00
  a
• 5:00
  lot
• 5:00
  of
• 5:00
  birds
• 5:01
  don't
• 5:01
  have
• 5:01
  much
• 5:02
  tissue
• 5:03
  in
• 5:03
  their
• 5:04
  legs
• 5:04
  or
• 5:04
  their
• 5:04
  feet.
• 5:05
  And
• 5:05
  there's
• 5:05
  not
• 5:05
  a
• 5:06
  lot
• 5:06
  of
• 5:06
  cells
• 5:07
  with
• 5:07
  a
• 5:07
  lot
• 5:07
  of
• 5:07
  fluid
• 5:08
  in
• 5:08
  there
• 5:09
  to
• 5:09
  freeze,
• 5:10
  just
• 5:11
  these
• 5:11
  tendons
• 5:11
  and
• 5:12
  these
• 5:12
  bones.
• 5:12
  And
• 5:12
  so
• 5:12
  that
• 5:13
  makes
• 5:13
  them
• 5:13
  less
• 5:13
  prone
• 5:14
  to
• 5:15
  frostbite,
• 5:16
  for
• 5:16
  instance.
• 5:17
  The
• 5:17
  final
• 5:17
  thing
• 5:18
  is
• 5:18
  that
• 5:18
  we
• 5:18
  think
• 5:18
  that
• 5:19
  birds
• 5:19
  just
• 5:19
  have
• 5:19
  fewer
• 5:20
  pain
• 5:20
  receptors
• 5:21
  in
• 5:21
  their
• 5:21
  feet
• 5:21
  than
• 5:21
  do
• 5:22
  you
• 5:22
  or
• 5:22
  I.
• 5:23
  And
• 5:23
  so
• 5:24
  these
• 5:24
  pain
• 5:25
  receptors
• 5:25
  are
• 5:25
  just
• 5:25
  a
• 5:26
  special
• 5:26
  kind
• 5:26
  of
• 5:26
  neuron
• 5:27
  that
• 5:27
  allow
• 5:27
  us
• 5:27
  to
• 5:28
  sense
• 5:28
  pain.
• 5:28
  And
• 5:29
  if
• 5:29
  we
• 5:29
  have
• 5:29
  fewer
• 5:29
  of
• 5:30
  them,
• 5:30
  we
• 5:30
  might
• 5:30
  be
• 5:30
  less
• 5:31
  sens
• 5:31
  to
• 5:31
  that
• 5:32
  pain
• 5:32
  overall.
• 5:33
  Yeah.
• 5:33
  So
• 5:34
  birds
• 5:34
  have
• 5:34
  cold
• 5:35
  feet,
• 5:35
  and
• 5:35
  that's
• 5:36
  on
• 5:36
  purpose.
• 5:36
  And
• 5:37
  it
• 5:37
  conserves
• 5:37
  heat
• 5:38
  in
• 5:38
  their
• 5:38
  body,
• 5:38
  which
• 5:38
  is
• 5:39
  really
• 5:39
  cool.
• 5:40
  I
• 5:40
  didn't
• 5:40
  know
• 5:40
  about
• 5:41
  the
• 5:41
  pain
• 5:41
  receptor
• 5:41
  thing.
• 5:41
  I
• 5:42
  would
• 5:42
  have
• 5:42
  appreciated
• 5:42
  that.
• 5:42
  I
• 5:43
  was
• 5:43
  a
• 5:43
  figure
• 5:43
  skater
• 5:44
  as
• 5:44
  a
• 5:44
  kid,
• 5:44
  and
• 5:45
  my
• 5:45
  biggest
• 5:45
  complaint
• 5:46
  was
• 5:46
  that
• 5:46
  my
• 5:46
  feet
• 5:46
  got
• 5:47
  way
• 5:47
  too
• 5:47
  cold,
• 5:48
  especially
• 5:48
  when
• 5:48
  I
• 5:49
  was
• 5:49
  a
• 5:49
  little
• 5:49
  kid
• 5:49
  who
• 5:50
  wasn't
• 5:50
  actually
• 5:51
  doing
• 5:51
  much
• 5:52
  on
• 5:52
  the
• 5:52
  ice,
• 5:52
  as
• 5:52
  it
• 5:53
  were.
• 5:53
  When
• 5:53
  we
• 5:53
  see
• 5:54
  birds
• 5:54
  legs
• 5:55
  and
• 5:55
  we
• 5:55
  think
• 5:55
  about
• 5:56
  how
• 5:56
  cold
• 5:56
  they
• 5:56
  must
• 5:56
  be,
• 5:56
  they
• 5:57
  actually
• 5:57
  are
• 5:57
  cold,
• 5:57
  but
• 5:58
  they're
• 5:58
  retaining
• 5:58
  heat
• 5:59
  in
• 5:59
  this
• 5:59
  really
• 5:59
  special
• 5:59
  way
• 6:00
  using
• 6:00
  countercurrent
• 6:00
  heat
• 6:00
  exchange.
• 6:01
  What
• 6:01
  are
• 6:02
  other
• 6:02
  ways
• 6:02
  that
• 6:02
  birds
• 6:03
  stay?
• 6:03
  You
• 6:04
  know,
• 6:04
  a
• 6:04
  lot
• 6:04
  of
• 6:04
  them
• 6:04
  leave
• 6:05
  for
• 6:05
  the
• 6:05
  winter,
• 6:05
  so
• 6:06
  those
• 6:06
  migrants
• 6:06
  don't
• 6:07
  have
• 6:07
  to
• 6:08
  deal
• 6:08
  with
• 6:08
  the
• 6:09
  cold.
• 6:09
  But
• 6:09
  we'll
• 6:09
  come
• 6:09
  back
• 6:10
  to
• 6:10
  that
• 6:10
  later
• 6:10
  based
• 6:10
  on
• 6:11
  some
• 6:11
  of
• 6:11
  your
• 6:11
  recent
• 6:11
  research
• 6:12
  and
• 6:12
  their,
• 6:12
  their
• 6:12
  ability
• 6:13
  to
• 6:13
  tolerate
• 6:13
  cold.
• 6:13
  But
• 6:14
  for
• 6:14
  the
• 6:14
  birds
• 6:14
  that
• 6:14
  stay
• 6:15
  and,
• 6:15
  and
• 6:15
  winter
• 6:16
  in
• 6:16
  places
• 6:17
  that
• 6:17
  are
• 6:17
  cold,
• 6:18
  what
• 6:18
  are
• 6:18
  their
• 6:18
  other
• 6:18
  strategies
• 6:19
  for
• 6:19
  staying
• 6:19
  warm?
• 6:20
  And
• 6:20
  how
• 6:20
  similar
• 6:21
  or
• 6:21
  different
• 6:21
  are
• 6:21
  those
• 6:22
  things
• 6:22
  to,
• 6:22
  like,
• 6:22
  how
• 6:22
  you
• 6:23
  and
• 6:23
  I
• 6:23
  try
• 6:23
  to
• 6:23
  stay
• 6:23
  warm?
• 6:24
  There's
• 6:24
  a
• 6:24
  lot
• 6:25
  of
• 6:25
  physiological
• 6:25
  strategies
• 6:26
  and
• 6:26
  then
• 6:26
  there's
• 6:26
  also
• 6:27
  behavioral
• 6:27
  strategies.
• 6:28
  And
• 6:28
  I'm
• 6:29
  a
• 6:29
  physiologist,
• 6:29
  so.
• 6:30
  So
• 6:30
  I'm
• 6:31
  gonna
• 6:31
  start
• 6:31
  with
• 6:31
  the
• 6:31
  physiology.
• 6:33
  So
• 6:33
  the
• 6:33
  biggest
• 6:33
  thing
• 6:34
  that
• 6:34
  birds
• 6:34
  do
• 6:34
  is
• 6:35
  that
• 6:35
  they
• 6:35
  shiver,
• 6:36
  just
• 6:36
  like
• 6:37
  you
• 6:37
  or
• 6:37
  I.
• 6:37
  So
• 6:38
  when
• 6:38
  they
• 6:38
  get
• 6:38
  really
• 6:38
  cold,
• 6:39
  they
• 6:39
  start
• 6:39
  shivering,
• 6:40
  and
• 6:40
  they're
• 6:40
  really
• 6:40
  good
• 6:41
  at
• 6:41
  shivering.
• 6:41
  So
• 6:42
  they
• 6:42
  use
• 6:42
  that
• 6:42
  really
• 6:42
  big
• 6:42
  breast
• 6:43
  muscle
• 6:43
  that
• 6:43
  they
• 6:43
  have,
• 6:44
  and
• 6:44
  they
• 6:44
  can
• 6:45
  just
• 6:45
  move
• 6:45
  it
• 6:45
  really
• 6:46
  quickly
• 6:46
  to
• 6:46
  generate
• 6:46
  a
• 6:47
  lot
• 6:47
  of
• 6:47
  heat.
• 6:48
  Another
• 6:48
  thing
• 6:49
  that
• 6:49
  they
• 6:49
  do
• 6:50
  is
• 6:50
  just
• 6:51
  the
• 6:52
  composition
• 6:52
  of
• 6:52
  their
• 6:53
  feathers.
• 6:53
  So
• 6:54
  feathers
• 6:54
  are
• 6:55
  really
• 6:55
  good
• 6:55
  insulators.
• 6:56
  That's
• 6:57
  why
• 6:57
  we
• 6:57
  use
• 6:57
  them
• 6:57
  in
• 6:57
  our
• 6:58
  blankets
• 6:58
  and
• 6:58
  our
• 6:58
  coats.
• 6:59
  We
• 6:59
  steal
• 7:00
  them
• 7:00
  for
• 7:00
  our
• 7:00
  own
• 7:01
  insulation.
• 7:01
  Ye,
• 7:02
  exactly.
• 7:02
  They're
• 7:03
  excellent
• 7:03
  at
• 7:03
  creating
• 7:04
  this
• 7:04
  barrier
• 7:04
  between
• 7:05
  the
• 7:05
  bird
• 7:06
  and
• 7:06
  the
• 7:06
  environment
• 7:07
  to
• 7:07
  trap
• 7:08
  warm
• 7:08
  air.
• 7:09
  And
• 7:09
  then
• 7:11
  each
• 7:11
  of
• 7:11
  those
• 7:11
  feathers
• 7:12
  at
• 7:12
  the
• 7:12
  base
• 7:13
  has
• 7:13
  a
• 7:13
  tiny
• 7:14
  little
• 7:14
  muscle
• 7:15
  that
• 7:15
  allows
• 7:15
  the
• 7:16
  bird
• 7:16
  to
• 7:16
  raise
• 7:16
  that
• 7:17
  feather
• 7:17
  or
• 7:17
  lower
• 7:18
  that
• 7:18
  feather.
• 7:18
  And
• 7:19
  so
• 7:19
  on
• 7:19
  a
• 7:19
  really
• 7:19
  cold
• 7:20
  day,
• 7:20
  you'll
• 7:20
  see
• 7:20
  that
• 7:21
  birds
• 7:21
  look
• 7:21
  especially
• 7:22
  fluffy.
• 7:23
  Sometimes
• 7:23
  they
• 7:23
  can
• 7:23
  even
• 7:24
  look
• 7:24
  round,
• 7:25
  like
• 7:25
  if
• 7:25
  you've
• 7:25
  ever
• 7:25
  seen
• 7:25
  a
• 7:26
  chickadee.
• 7:26
  And
• 7:26
  it's
• 7:26
  like
• 7:26
  a
• 7:27
  ball
• 7:27
  because
• 7:28
  they
• 7:28
  have
• 7:28
  all
• 7:28
  of
• 7:29
  those
• 7:29
  muscles
• 7:30
  erecting
• 7:31
  those
• 7:31
  feathers
• 7:32
  and
• 7:32
  creating
• 7:32
  this
• 7:32
  really
• 7:33
  large
• 7:33
  barrier
• 7:34
  around
• 7:35
  them
• 7:35
  to
• 7:35
  trap
• 7:35
  heat.
• 7:36
  Yeah.
• 7:36
  And
• 7:36
  it's
• 7:36
  interesting
• 7:37
  to
• 7:37
  think
• 7:37
  about
• 7:37
  the
• 7:37
  feathers
• 7:38
  because
• 7:38
  I
• 7:39
  think
• 7:39
  a
• 7:39
  lot
• 7:39
  of
• 7:39
  people
• 7:40
  contemporarily
• 7:40
  associate
• 7:41
  feathers
• 7:41
  in
• 7:42
  birds,
• 7:42
  which
• 7:42
  makes
• 7:43
  sense.
• 7:43
  Birds
• 7:43
  are
• 7:43
  the
• 7:44
  only
• 7:44
  creatures
• 7:44
  on
• 7:44
  the
• 7:44
  planet
• 7:45
  that
• 7:45
  have
• 7:45
  feathers.
• 7:46
  But
• 7:47
  we
• 7:47
  also
• 7:47
  tend
• 7:48
  to
• 7:48
  think
• 7:48
  then
• 7:48
  feathers
• 7:49
  are
• 7:49
  directly
• 7:49
  associated
• 7:50
  with
• 7:50
  flight.
• 7:51
  And
• 7:51
  it's
• 7:51
  more
• 7:52
  likely
• 7:52
  that
• 7:52
  feathers
• 7:53
  were
• 7:53
  initially
• 7:53
  this
• 7:54
  thermal
• 7:54
  regulation
• 7:55
  or
• 7:56
  insulatory
• 7:56
  thing
• 7:57
  that
• 7:57
  evolved
• 7:57
  and
• 7:58
  then
• 7:58
  secondarily
• 7:58
  became
• 7:59
  important
• 7:59
  for
• 8:00
  flight,
• 8:00
  which
• 8:00
  is,
• 8:01
  uh,
• 8:01
  yeah,
• 8:01
  cool
• 8:02
  to
• 8:02
  think
• 8:02
  about.
• 8:02
  They're
• 8:03
  very
• 8:03
  good
• 8:03
  insulators,
• 8:04
  for
• 8:04
  sure,
• 8:04
  in
• 8:05
  the
• 8:05
  context
• 8:05
  of
• 8:05
  shivering.
• 8:05
  So
• 8:06
  you're
• 8:06
  talking
• 8:06
  about
• 8:06
  the
• 8:06
  fact
• 8:06
  that
• 8:07
  birds
• 8:07
  have
• 8:08
  these
• 8:08
  large
• 8:08
  pectoral
• 8:09
  muscles.
• 8:09
  And
• 8:09
  I
• 8:09
  think
• 8:10
  it's
• 8:10
  important
• 8:10
  to
• 8:10
  point
• 8:10
  out,
• 8:11
  like
• 8:11
  to
• 8:11
  folks
• 8:12
  listening,
• 8:12
  that
• 8:12
  birds
• 8:13
  have
• 8:14
  gigantic
• 8:15
  pectoral
• 8:16
  muscles.
• 8:16
  Even
• 8:17
  the
• 8:17
  most
• 8:17
  basic
• 8:18
  bird
• 8:18
  that
• 8:18
  you
• 8:19
  wouldn't
• 8:19
  assume,
• 8:19
  like,
• 8:20
  not
• 8:20
  a.
• 8:21
  A
• 8:21
  turkey
• 8:21
  that
• 8:21
  we've
• 8:22
  bred
• 8:22
  to
• 8:22
  have
• 8:22
  big
• 8:23
  peck
• 8:23
  mussels
• 8:23
  so
• 8:24
  we
• 8:24
  can
• 8:24
  eat
• 8:24
  them.
• 8:24
  Or
• 8:24
  the
• 8:24
  breast
• 8:25
  muscles,
• 8:25
  like
• 8:25
  the
• 8:26
  proportion
• 8:26
  of
• 8:26
  a
• 8:26
  human's
• 8:27
  body
• 8:27
  that
• 8:27
  is
• 8:27
  muscles
• 8:29
  is
• 8:30
  quite
• 8:30
  small
• 8:31
  actually.
• 8:31
  Even
• 8:32
  like
• 8:32
  for
• 8:32
  a
• 8:32
  bodybuilder,
• 8:33
  the
• 8:33
  overall
• 8:33
  proportion
• 8:34
  is
• 8:34
  small.
• 8:34
  But
• 8:34
  for
• 8:34
  the
• 8:35
  average
• 8:35
  bird,
• 8:36
  the
• 8:36
  pectoral
• 8:37
  muscles
• 8:37
  are
• 8:37
  like
• 8:37
  up
• 8:38
  to
• 8:38
  40%
• 8:39
  of
• 8:39
  the
• 8:39
  body
• 8:39
  mass.
• 8:40
  Right.
• 8:40
  So
• 8:40
  we're
• 8:40
  talking
• 8:40
  like
• 8:41
  these
• 8:41
  gigantic
• 8:42
  muscles.
• 8:42
  Yeah,
• 8:43
  they
• 8:43
  can
• 8:43
  also
• 8:43
  use
• 8:44
  muscles
• 8:44
  in
• 8:44
  their
• 8:44
  legs
• 8:45
  and
• 8:45
  in
• 8:45
  their
• 8:45
  wings
• 8:46
  as
• 8:46
  well.
• 8:46
  But
• 8:47
  the
• 8:47
  principal
• 8:49
  heat
• 8:49
  is
• 8:49
  coming
• 8:50
  from
• 8:50
  that
• 8:50
  pectoralis
• 8:51
  muscle
• 8:51
  because
• 8:52
  it's
• 8:52
  so
• 8:52
  large.
• 8:54
  And
• 8:54
  it's
• 8:54
  cool
• 8:54
  that,
• 8:54
  like,
• 8:55
  it's
• 8:55
  large
• 8:55
  in
• 8:55
  part.
• 8:56
  Well,
• 8:56
  mostly
• 8:56
  because
• 8:57
  of
• 8:57
  flight.
• 8:57
  But
• 8:57
  then
• 8:57
  there's
• 8:58
  this
• 8:58
  amazing
• 8:59
  ability
• 8:59
  to
• 8:59
  use
• 8:59
  it
• 9:00
  to
• 9:00
  generate
• 9:00
  heat
• 9:00
  and
• 9:01
  survive
• 9:01
  cold
• 9:01
  temperatures.
• 9:02
  Yeah.
• 9:02
  So,
• 9:03
  okay,
• 9:03
  if
• 9:03
  heat's
• 9:03
  coming
• 9:04
  from
• 9:04
  shivering
• 9:05
  in
• 9:05
  birds
• 9:06
  and
• 9:06
  then
• 9:06
  being
• 9:07
  retained
• 9:07
  using
• 9:08
  the
• 9:08
  feathers,
• 9:10
  what
• 9:10
  is
• 9:10
  the
• 9:10
  cost
• 9:10
  of
• 9:11
  that?
• 9:11
  Like,
• 9:11
  on
• 9:12
  a
• 9:12
  typical
• 9:12
  day,
• 9:12
  you
• 9:12
  know,
• 9:12
  a
• 9:13
  chickadee
• 9:13
  is
• 9:13
  what,
• 9:13
  10
• 9:14
  to
• 9:14
  12
• 9:14
  grams?
• 9:15
  It
• 9:15
  has
• 9:15
  to
• 9:15
  maintain
• 9:16
  a
• 9:16
  body
• 9:16
  temperature
• 9:16
  slightly
• 9:17
  higher
• 9:17
  than
• 9:17
  you
• 9:17
  and
• 9:17
  I.
• 9:18
  So
• 9:18
  what's
• 9:18
  the,
• 9:18
  like,
• 9:19
  metabolic
• 9:19
  cost
• 9:20
  given
• 9:20
  that
• 9:20
  you're,
• 9:20
  you
• 9:20
  know,
• 9:21
  let's
• 9:21
  get
• 9:21
  into
• 9:21
  the
• 9:21
  physiology
• 9:22
  of
• 9:22
  it.
• 9:22
  Yeah.
• 9:23
  So
• 9:23
  birds
• 9:24
  spend
• 9:24
  a
• 9:24
  lot
• 9:25
  of
• 9:25
  time
• 9:25
  eating
• 9:26
  when
• 9:26
  it's
• 9:26
  cold
• 9:26
  out
• 9:27
  if
• 9:27
  you
• 9:27
  have
• 9:28
  a
• 9:28
  bird
• 9:28
  feeder,
• 9:28
  you
• 9:28
  probably
• 9:29
  noticed
• 9:29
  this,
• 9:29
  right?
• 9:29
  Like
• 9:30
  they
• 9:30
  are
• 9:30
  out
• 9:30
  there
• 9:31
  all
• 9:31
  the
• 9:31
  time
• 9:31
  eating
• 9:32
  and
• 9:32
  on
• 9:32
  cold
• 9:32
  days
• 9:33
  they
• 9:33
  need
• 9:34
  to
• 9:34
  stock
• 9:34
  up
• 9:35
  for
• 9:35
  their
• 9:36
  night.
• 9:37
  So
• 9:37
  you
• 9:37
  will
• 9:37
  see
• 9:38
  birds
• 9:38
  feeding
• 9:39
  and
• 9:39
  some
• 9:39
  species
• 9:40
  do
• 9:40
  this
• 9:40
  later
• 9:41
  than
• 9:41
  others.
• 9:41
  You'll
• 9:42
  see
• 9:42
  them
• 9:42
  feeding
• 9:42
  at
• 9:42
  the
• 9:42
  very
• 9:43
  end
• 9:43
  of
• 9:43
  the
• 9:43
  day.
• 9:43
  Sometimes,
• 9:44
  just
• 9:44
  as
• 9:44
  it's
• 9:44
  getting
• 9:45
  dark,
• 9:45
  I'll
• 9:46
  still
• 9:46
  have
• 9:46
  a
• 9:46
  couple
• 9:46
  cardinals
• 9:47
  out
• 9:47
  and
• 9:48
  they'll
• 9:48
  be
• 9:49
  packing
• 9:50
  on
• 9:50
  fat
• 9:50
  so
• 9:50
  that
• 9:51
  they
• 9:51
  can
• 9:52
  generate
• 9:52
  heat
• 9:53
  all
• 9:53
  night
• 9:53
  long.
• 9:54
  And
• 9:54
  it's
• 9:54
  really
• 9:55
  a
• 9:55
  balance
• 9:56
  for
• 9:56
  birds
• 9:56
  between
• 9:57
  how
• 9:58
  much
• 9:58
  time
• 9:58
  they're
• 9:59
  going
• 9:59
  to
• 9:59
  spend
• 9:59
  eating
• 10:00
  and
• 10:01
  exposing
• 10:01
  themselves
• 10:02
  potentially
• 10:02
  to
• 10:02
  predators
• 10:03
  while
• 10:03
  they're
• 10:03
  at
• 10:04
  those
• 10:04
  feeders
• 10:05
  and
• 10:06
  how
• 10:06
  much
• 10:07
  energy
• 10:07
  they
• 10:07
  think
• 10:08
  they
• 10:08
  might
• 10:08
  need
• 10:08
  to
• 10:09
  survive
• 10:09
  that
• 10:09
  night.
• 10:09
  Because
• 10:10
  they
• 10:10
  don't
• 10:10
  really
• 10:10
  know
• 10:10
  how
• 10:11
  cold
• 10:11
  it's
• 10:11
  going
• 10:11
  to
• 10:11
  get
• 10:11
  or
• 10:12
  how
• 10:12
  much
• 10:13
  fat
• 10:13
  they're
• 10:13
  going
• 10:13
  to
• 10:13
  burn.
• 10:14
  Because
• 10:14
  I
• 10:15
  should
• 10:15
  mention
• 10:15
  that
• 10:15
  birds
• 10:16
  are
• 10:16
  principally
• 10:16
  using
• 10:17
  fat
• 10:17
  when
• 10:18
  they're
• 10:18
  shivering.
• 10:19
  So
• 10:19
  they're
• 10:19
  really
• 10:20
  good
• 10:20
  at
• 10:20
  using
• 10:21
  up
• 10:21
  fat
• 10:22
  overnight.
• 10:22
  And
• 10:23
  so
• 10:23
  there
• 10:23
  has
• 10:23
  been
• 10:23
  some
• 10:24
  work
• 10:24
  showing
• 10:26
  how
• 10:27
  exactly
• 10:27
  how
• 10:28
  much
• 10:28
  fat
• 10:29
  they
• 10:29
  need
• 10:29
  to
• 10:29
  put
• 10:29
  on
• 10:30
  overnight
• 10:31
  depending
• 10:32
  on
• 10:32
  the
• 10:32
  temperature
• 10:32
  that
• 10:33
  they're
• 10:33
  exposed
• 10:33
  to
• 10:33
  the
• 10:34
  next
• 10:34
  day.
• 10:36
  And
• 10:37
  it's
• 10:37
  quite
• 10:38
  a
• 10:38
  bit.
• 10:38
  So
• 10:38
  it
• 10:38
  can
• 10:39
  be
• 10:39
  grams,
• 10:39
  like
• 10:39
  you're
• 10:40
  saying
• 10:40
  a
• 10:40
  chickadee
• 10:41
  that
• 10:41
  weighs
• 10:41
  10
• 10:42
  grams
• 10:42
  might
• 10:42
  need
• 10:43
  to
• 10:43
  put
• 10:43
  on
• 10:43
  whole
• 10:44
  gram
• 10:44
  before
• 10:46
  going
• 10:46
  to
• 10:46
  sleep
• 10:46
  at
• 10:46
  night.
• 10:47
  And
• 10:47
  if
• 10:47
  they
• 10:47
  get
• 10:47
  it
• 10:47
  wrong,
• 10:48
  like
• 10:49
  the
• 10:49
  consequences
• 10:50
  are
• 10:50
  really
• 10:50
  serious.
• 10:51
  So
• 10:51
  they
• 10:51
  might
• 10:51
  not
• 10:51
  wake
• 10:52
  up
• 10:52
  in
• 10:52
  the
• 10:52
  morning
• 10:52
  if
• 10:53
  they
• 10:53
  didn't
• 10:53
  pack
• 10:53
  on
• 10:54
  enough
• 10:54
  fat
• 10:54
  to
• 10:54
  stay
• 10:55
  warm
• 10:55
  overnight.
• 10:56
  That's
• 10:56
  also
• 10:56
  why
• 10:56
  you
• 10:56
  see
• 10:57
  kind
• 10:57
  of
• 10:57
  a
• 10:57
  flush
• 10:57
  of
• 10:57
  feeder
• 10:58
  activity
• 10:58
  right
• 10:59
  away
• 10:59
  in
• 10:59
  the
• 10:59
  morning
• 11:00
  because
• 11:00
  they're
• 11:00
  all
• 11:00
  like
• 11:01
  trying
• 11:01
  to
• 11:01
  restock.
• 11:02
  Yeah,
• 11:03
  yeah,
• 11:03
  exactly.
• 11:04
  It's
• 11:04
  amazing
• 11:05
  the
• 11:05
  kind
• 11:05
  of
• 11:06
  the
• 11:06
  knife's
• 11:06
  edge
• 11:06
  that
• 11:07
  a
• 11:07
  lot
• 11:07
  of
• 11:07
  these
• 11:07
  birds
• 11:08
  live
• 11:08
  on
• 11:08
  because
• 11:08
  they
• 11:09
  have
• 11:09
  to
• 11:09
  put
• 11:09
  on
• 11:10
  fat,
• 11:10
  but
• 11:10
  not
• 11:11
  so
• 11:11
  much
• 11:11
  fat
• 11:11
  that
• 11:11
  they
• 11:11
  can't
• 11:11
  fly
• 11:12
  because
• 11:12
  then
• 11:12
  they'll
• 11:13
  be
• 11:13
  consequences
• 11:14
  for
• 11:14
  that.
• 11:14
  Obviously
• 11:15
  in
• 11:15
  terms
• 11:15
  of
• 11:15
  predator
• 11:15
  avoidance.
• 11:16
  I
• 11:17
  mean,
• 11:17
  this
• 11:17
  is
• 11:17
  one
• 11:17
  of
• 11:17
  the
• 11:17
  things
• 11:18
  that
• 11:18
  interests
• 11:19
  me
• 11:19
  most
• 11:20
  about
• 11:20
  animals
• 11:21
  is
• 11:21
  their
• 11:21
  ability
• 11:22
  to
• 11:22
  adjust
• 11:22
  to
• 11:22
  these
• 11:23
  changing
• 11:23
  conditions
• 11:24
  and
• 11:26
  for
• 11:26
  temperature.
• 11:27
  With
• 11:27
  birds,
• 11:28
  they're
• 11:28
  making
• 11:28
  a
• 11:29
  lot
• 11:29
  of
• 11:29
  changes
• 11:30
  across
• 11:31
  different
• 11:31
  levels
• 11:31
  of
• 11:31
  their
• 11:32
  body.
• 11:32
  So
• 11:33
  the
• 11:33
  ability
• 11:34
  to
• 11:34
  shiver
• 11:35
  more
• 11:35
  when
• 11:36
  it's
• 11:36
  cold
• 11:37
  comes
• 11:37
  from
• 11:38
  changes
• 11:38
  that
• 11:38
  are
• 11:39
  happening
• 11:39
  within
• 11:39
  the
• 11:40
  muscle,
• 11:41
  but
• 11:41
  also
• 11:42
  changes
• 11:42
  that
• 11:42
  are
• 11:42
  happening
• 11:43
  within
• 11:43
  their
• 11:43
  digestive
• 11:44
  system
• 11:44
  and
• 11:45
  within
• 11:45
  their
• 11:46
  cardiovascular
• 11:47
  system.
• 11:48
  So
• 11:48
  one
• 11:49
  thing
• 11:49
  that
• 11:49
  I
• 11:49
  found,
• 11:50
  and
• 11:50
  others
• 11:50
  have
• 11:51
  found
• 11:51
  this
• 11:51
  too,
• 11:51
  is
• 11:51
  that
• 11:52
  a
• 11:52
  lot
• 11:53
  of
• 11:53
  birds
• 11:53
  can
• 11:53
  increase
• 11:54
  the
• 11:54
  size
• 11:54
  of
• 11:54
  their
• 11:54
  heart
• 11:55
  when
• 11:55
  they're
• 11:55
  exposed
• 11:55
  to
• 11:56
  cold
• 11:56
  temperatures.
• 11:57
  And
• 11:57
  this
• 11:57
  can
• 11:57
  happen
• 11:58
  in
• 11:58
  a
• 11:58
  matter
• 11:58
  of
• 11:58
  days
• 11:59
  really.
• 12:00
  So
• 12:00
  dark
• 12:00
  eyed
• 12:01
  juncos,
• 12:01
  which
• 12:01
  I
• 12:02
  spend
• 12:02
  a
• 12:02
  Lot
• 12:02
  of
• 12:02
  time
• 12:02
  thinking
• 12:03
  about
• 12:03
  they
• 12:04
  increase
• 12:04
  the
• 12:04
  size
• 12:04
  of
• 12:05
  their
• 12:05
  heart
• 12:05
  by
• 12:05
  25%
• 12:06
  in
• 12:07
  as
• 12:07
  little
• 12:07
  as
• 12:07
  a
• 12:07
  week
• 12:07
  when
• 12:08
  you
• 12:08
  expose
• 12:08
  them
• 12:08
  to
• 12:09
  really
• 12:09
  cold
• 12:09
  temperatures.
• 12:10
  And
• 12:10
  that
• 12:10
  would
• 12:10
  be
• 12:11
  a
• 12:11
  really
• 12:11
  bad
• 12:12
  thing
• 12:12
  in
• 12:12
  a
• 12:12
  human.
• 12:13
  Like,
• 12:14
  having
• 12:14
  cardiac
• 12:15
  hypertrophy
• 12:16
  is
• 12:16
  generally
• 12:17
  not
• 12:18
  good
• 12:18
  for
• 12:18
  your
• 12:18
  health.
• 12:19
  But
• 12:19
  birds
• 12:20
  seem
• 12:20
  to
• 12:20
  be
• 12:20
  able
• 12:20
  to
• 12:21
  flexibly
• 12:21
  change
• 12:22
  the
• 12:22
  size
• 12:22
  of
• 12:22
  their
• 12:23
  heart
• 12:23
  quite
• 12:23
  a
• 12:24
  lot.
• 12:25
  They're
• 12:25
  also
• 12:26
  making
• 12:26
  changes
• 12:28
  to
• 12:28
  their
• 12:28
  digestive
• 12:29
  tract
• 12:29
  that
• 12:29
  allow
• 12:29
  them
• 12:29
  to
• 12:30
  eat
• 12:30
  more
• 12:30
  food.
• 12:31
  So
• 12:31
  growing
• 12:32
  the
• 12:32
  size
• 12:32
  of
• 12:32
  their
• 12:34
  gizzard
• 12:34
  or
• 12:34
  stomach
• 12:35
  in
• 12:35
  their
• 12:35
  intestines
• 12:36
  and
• 12:37
  often
• 12:38
  increasing
• 12:39
  the
• 12:39
  efficiency
• 12:40
  of
• 12:40
  the
• 12:40
  intestine
• 12:41
  to
• 12:41
  actually
• 12:41
  extract
• 12:42
  nutrients
• 12:42
  from
• 12:43
  their
• 12:43
  food.
• 12:44
  And
• 12:44
  then
• 12:44
  we
• 12:44
  also
• 12:45
  see
• 12:45
  changes
• 12:45
  at
• 12:46
  the
• 12:46
  cellular
• 12:46
  level
• 12:47
  in
• 12:48
  the
• 12:48
  muscle.
• 12:48
  So
• 12:49
  some
• 12:49
  birds
• 12:50
  not
• 12:51
  only
• 12:51
  grow
• 12:51
  the
• 12:51
  size
• 12:52
  of
• 12:52
  their
• 12:52
  muscle
• 12:53
  in
• 12:53
  the
• 12:53
  winter,
• 12:53
  so
• 12:54
  a
• 12:54
  lot
• 12:54
  of
• 12:54
  them
• 12:54
  make
• 12:54
  that
• 12:55
  pectoralis
• 12:55
  larger,
• 12:56
  but
• 12:56
  they'll
• 12:57
  actually
• 12:57
  change
• 12:59
  the
• 12:59
  muscle
• 12:59
  cells
• 13:00
  so
• 13:00
  that
• 13:01
  oxygen
• 13:02
  can
• 13:02
  diffuse
• 13:02
  more
• 13:02
  efficiently.
• 13:03
  Or
• 13:05
  they
• 13:05
  might
• 13:05
  increase
• 13:05
  the
• 13:06
  number
• 13:06
  of
• 13:07
  blood
• 13:07
  vessels,
• 13:08
  capillaries
• 13:08
  that
• 13:09
  are
• 13:09
  feeding
• 13:09
  that
• 13:09
  muscle
• 13:10
  to
• 13:10
  get
• 13:10
  oxygen
• 13:11
  and
• 13:12
  fuels
• 13:13
  to
• 13:13
  that
• 13:13
  muscle
• 13:14
  more
• 13:14
  efficiently.
• 13:15
  That's
• 13:15
  really
• 13:15
  cool.
• 13:15
  I
• 13:16
  mean,
• 13:16
  I
• 13:16
  think
• 13:16
  we
• 13:16
  tend
• 13:16
  to
• 13:17
  think
• 13:17
  as
• 13:17
  humans,
• 13:18
  like,
• 13:18
  our
• 13:18
  bodies
• 13:19
  don't
• 13:19
  change
• 13:19
  that
• 13:20
  much
• 13:20
  past
• 13:20
  a
• 13:20
  certain
• 13:21
  age
• 13:21
  unless
• 13:21
  we're
• 13:21
  like,
• 13:22
  I'm
• 13:22
  going
• 13:22
  to
• 13:22
  bulk
• 13:22
  up
• 13:23
  and
• 13:23
  put
• 13:23
  on
• 13:24
  a
• 13:24
  lot
• 13:24
  of
• 13:24
  muscle
• 13:24
  mass.
• 13:24
  And
• 13:25
  that
• 13:25
  takes
• 13:25
  them
• 13:25
  time,
• 13:25
  maybe
• 13:26
  more
• 13:26
  effort
• 13:26
  than
• 13:26
  we
• 13:27
  would
• 13:27
  like
• 13:27
  at,
• 13:27
  you
• 13:28
  know,
• 13:28
  especially
• 13:28
  in
• 13:29
  our
• 13:29
  40s.
• 13:30
  It's
• 13:30
  amazing
• 13:31
  to
• 13:31
  think
• 13:31
  about
• 13:31
  how,
• 13:32
  like,
• 13:32
  malleable
• 13:33
  or
• 13:33
  reactive
• 13:34
  to
• 13:34
  the
• 13:34
  environment
• 13:34
  organ
• 13:35
  systems
• 13:35
  are
• 13:36
  in
• 13:36
  birds
• 13:37
  like
• 13:37
  you
• 13:37
  just
• 13:37
  described,
• 13:38
  changes
• 13:39
  to
• 13:39
  heart,
• 13:39
  which
• 13:39
  would
• 13:39
  be
• 13:40
  impossible
• 13:40
  to
• 13:40
  imagine
• 13:40
  in
• 13:41
  humans
• 13:41
  unless
• 13:41
  you
• 13:41
  were
• 13:42
  in
• 13:42
  some
• 13:42
  insane
• 13:43
  disease
• 13:43
  state,
• 13:44
  like
• 13:44
  end
• 13:44
  stages
• 13:45
  of
• 13:45
  that
• 13:45
  disease,
• 13:46
  or
• 13:46
  like
• 13:47
  your
• 13:47
  GI
• 13:47
  system,
• 13:48
  like
• 13:48
  enlarging
• 13:49
  and
• 13:49
  changing
• 13:49
  the
• 13:49
  way
• 13:50
  it's
• 13:50
  absorbing
• 13:50
  nutrients.
• 13:51
  And
• 13:51
  so
• 13:51
  such
• 13:51
  a
• 13:51
  rapid
• 13:52
  response
• 13:52
  to
• 13:52
  cold
• 13:53
  is
• 13:53
  super
• 13:53
  fascinating.
• 13:54
  I
• 13:54
  agree.
• 13:55
  Yeah.
• 13:55
  I
• 13:56
  think
• 13:56
  that
• 13:57
  there
• 13:58
  are
• 13:58
  mammals
• 13:58
  that
• 13:58
  can
• 13:59
  do
• 14:00
  some
• 14:00
  of
• 14:00
  these
• 14:01
  rapid
• 14:02
  changes
• 14:02
  as
• 14:03
  well,
• 14:04
  but
• 14:04
  I
• 14:04
  think
• 14:04
  birds
• 14:05
  and
• 14:05
  reptiles
• 14:06
  are
• 14:06
  especially
• 14:07
  good
• 14:07
  at
• 14:07
  it.
• 14:08
  So
• 14:08
  these
• 14:09
  changes
• 14:09
  in
• 14:09
  the
• 14:09
  digestive
• 14:10
  tract
• 14:10
  are
• 14:10
  very
• 14:10
  similar
• 14:11
  to
• 14:11
  pythons,
• 14:12
  which
• 14:12
  are
• 14:14
  the
• 14:15
  example
• 14:15
  of
• 14:16
  not
• 14:16
  eating
• 14:16
  for
• 14:17
  months.
• 14:17
  They
• 14:18
  totally
• 14:19
  reduce
• 14:19
  the
• 14:19
  size
• 14:19
  of
• 14:19
  the
• 14:19
  digestive
• 14:20
  tract,
• 14:20
  and
• 14:20
  then
• 14:20
  within
• 14:21
  24
• 14:21
  hours,
• 14:21
  they
• 14:21
  can
• 14:22
  regrow
• 14:22
  the
• 14:22
  whole
• 14:22
  thing.
• 14:24
  Birds
• 14:24
  aren't
• 14:25
  doing
• 14:25
  it
• 14:25
  quite
• 14:25
  at
• 14:25
  that
• 14:26
  level,
• 14:26
  but
• 14:26
  they're
• 14:26
  still
• 14:27
  pretty
• 14:27
  impressive.
• 14:27
  Yeah.
• 14:28
  But
• 14:28
  birds
• 14:29
  also
• 14:29
  have
• 14:29
  a
• 14:29
  couple
• 14:29
  other
• 14:30
  strategies
• 14:33
  for
• 14:33
  handling
• 14:34
  these
• 14:34
  really
• 14:34
  cold
• 14:34
  temperatures,
• 14:35
  and
• 14:35
  chickadees
• 14:36
  are
• 14:36
  a
• 14:36
  great
• 14:36
  example
• 14:36
  of
• 14:37
  that.
• 14:37
  So
• 14:38
  if
• 14:38
  they
• 14:39
  can't
• 14:39
  put
• 14:39
  on
• 14:40
  enough
• 14:40
  fat,
• 14:41
  then
• 14:41
  they
• 14:41
  might
• 14:41
  instead
• 14:42
  choose
• 14:43
  to
• 14:43
  drop
• 14:43
  their
• 14:44
  body
• 14:44
  temperature.
• 14:45
  So
• 14:46
  stay,
• 14:48
  stay
• 14:48
  cooler
• 14:49
  than
• 14:49
  you
• 14:49
  might
• 14:49
  expect
• 14:50
  overnight.
• 14:50
  And
• 14:50
  this
• 14:51
  allows
• 14:51
  them
• 14:51
  to
• 14:51
  then
• 14:52
  save
• 14:52
  energy
• 14:54
  and
• 14:54
  in
• 14:54
  the
• 14:55
  morning,
• 14:55
  then
• 14:55
  they
• 14:55
  have
• 14:56
  to
• 14:56
  use
• 14:56
  a
• 14:56
  little
• 14:56
  bit
• 14:56
  more
• 14:57
  energy
• 14:57
  to
• 14:57
  warm
• 14:57
  up
• 14:57
  than
• 14:58
  they
• 14:58
  otherwise
• 14:58
  would.
• 14:59
  But
• 14:59
  overall
• 14:59
  it
• 15:00
  could
• 15:00
  be
• 15:00
  an
• 15:01
  energy
• 15:01
  saving
• 15:01
  strategy
• 15:02
  for
• 15:02
  them.
• 15:03
  And
• 15:03
  that's
• 15:04
  called
• 15:04
  torpor,
• 15:05
  right?
• 15:05
  Yeah,
• 15:05
  yeah,
• 15:06
  it's
• 15:06
  called
• 15:06
  torpor.
• 15:07
  So
• 15:08
  poorwills
• 15:08
  can
• 15:08
  go
• 15:09
  into
• 15:09
  torpor
• 15:10
  for
• 15:12
  like
• 15:12
  three
• 15:12
  days
• 15:12
  at
• 15:13
  a
• 15:13
  time
• 15:14
  and
• 15:15
  then
• 15:16
  they'll
• 15:16
  actually
• 15:17
  stay
• 15:17
  inactive
• 15:18
  for
• 15:18
  up
• 15:18
  to
• 15:18
  45
• 15:19
  days.
• 15:20
  So
• 15:20
  really
• 15:21
  in
• 15:21
  those
• 15:21
  45
• 15:22
  days
• 15:22
  they'll
• 15:22
  like
• 15:23
  come
• 15:23
  out
• 15:23
  of
• 15:23
  the
• 15:23
  torpor
• 15:24
  and
• 15:24
  go
• 15:24
  back
• 15:24
  into
• 15:24
  the
• 15:24
  torpor.
• 15:26
  And
• 15:26
  there
• 15:27
  was
• 15:27
  a
• 15:27
  recent
• 15:27
  study
• 15:28
  that
• 15:28
  showed
• 15:29
  that
• 15:29
  they
• 15:30
  often
• 15:31
  find
• 15:31
  places
• 15:32
  to
• 15:32
  roost
• 15:34
  that
• 15:34
  are
• 15:34
  exposed,
• 15:36
  but
• 15:36
  they'll
• 15:37
  face
• 15:37
  sunlight
• 15:38
  in
• 15:38
  like
• 15:38
  the
• 15:38
  late
• 15:39
  afternoon.
• 15:39
  And
• 15:39
  that'll
• 15:40
  help
• 15:40
  them
• 15:40
  warm
• 15:41
  up
• 15:41
  out
• 15:41
  of
• 15:41
  these
• 15:42
  torpor
• 15:42
  bouts
• 15:43
  sort
• 15:43
  of
• 15:43
  naturally
• 15:44
  with
• 15:44
  the
• 15:44
  sunlight.
• 15:45
  And
• 15:45
  if
• 15:46
  they
• 15:46
  shaded
• 15:47
  the
• 15:47
  bird,
• 15:47
  then
• 15:47
  they
• 15:47
  had
• 15:48
  more
• 15:48
  trouble
• 15:49
  coming
• 15:49
  out
• 15:49
  of
• 15:49
  those
• 15:50
  torpor
• 15:50
  bouts.
• 15:51
  I
• 15:51
  had
• 15:51
  no
• 15:51
  idea.
• 15:52
  That's
• 15:53
  like
• 15:53
  the
• 15:53
  only
• 15:53
  example
• 15:54
  of
• 15:54
  hibernation
• 15:55
  in
• 15:56
  birds
• 15:56
  that
• 15:56
  I'm
• 15:56
  aware
• 15:56
  of.
• 16:00
  I
• 16:00
  mean,
• 16:00
  I
• 16:01
  think
• 16:01
  juncos
• 16:01
  are
• 16:01
  amazing.
• 16:02
  So
• 16:02
  on
• 16:02
  the
• 16:02
  coldest
• 16:03
  mornings
• 16:03
  you
• 16:03
  still
• 16:03
  see
• 16:04
  them
• 16:04
  active
• 16:04
  at
• 16:04
  your
• 16:04
  bird
• 16:05
  feeder.
• 16:05
  And
• 16:06
  that's
• 16:06
  true
• 16:06
  of
• 16:06
  a
• 16:06
  lot
• 16:06
  of
• 16:07
  birds.
• 16:07
  But
• 16:07
  sometimes
• 16:07
  I
• 16:08
  think
• 16:08
  there
• 16:08
  are
• 16:08
  some
• 16:08
  birds
• 16:09
  that
• 16:09
  sleep
• 16:09
  in
• 16:09
  a
• 16:10
  little
• 16:10
  bit
• 16:10
  maybe
• 16:11
  because
• 16:11
  they're
• 16:11
  taking
• 16:11
  longer
• 16:12
  to
• 16:12
  wake
• 16:12
  up
• 16:12
  and
• 16:13
  drunkards
• 16:14
  are
• 16:14
  always
• 16:14
  out
• 16:15
  there
• 16:16
  and
• 16:17
  they're
• 16:18
  all
• 16:18
  over
• 16:18
  the
• 16:18
  place.
• 16:19
  So
• 16:19
  some
• 16:19
  of
• 16:19
  them
• 16:19
  are
• 16:20
  wintering
• 16:20
  in
• 16:21
  our
• 16:22
  southern
• 16:22
  states
• 16:22
  and
• 16:22
  some
• 16:23
  of
• 16:23
  them
• 16:23
  are
• 16:23
  wintering
• 16:24
  up
• 16:24
  into
• 16:24
  Canada.
• 16:25
  So
• 16:25
  I
• 16:25
  think
• 16:26
  they're
• 16:26
  a
• 16:26
  really
• 16:26
  good
• 16:27
  example
• 16:27
  of
• 16:29
  sort
• 16:29
  of
• 16:29
  differences
• 16:30
  in
• 16:30
  cold
• 16:30
  tolerances
• 16:31
  within
• 16:32
  the
• 16:32
  single
• 16:32
  species,
• 16:33
  which
• 16:33
  is
• 16:33
  why
• 16:33
  I
• 16:34
  study
• 16:34
  them.
• 16:35
  One
• 16:35
  thing
• 16:35
  that
• 16:36
  you
• 16:36
  don't
• 16:36
  see
• 16:36
  juncos
• 16:37
  doing
• 16:37
  that
• 16:38
  some
• 16:39
  birds
• 16:39
  do
• 16:39
  do.
• 16:39
  And
• 16:40
  I've
• 16:40
  always
• 16:40
  been
• 16:40
  interested
• 16:41
  to
• 16:41
  find
• 16:41
  a
• 16:42
  junco
• 16:42
  is
• 16:42
  like,
• 16:42
  what
• 16:43
  do
• 16:43
  they
• 16:43
  do
• 16:43
  at
• 16:43
  night?
• 16:44
  Right.
• 16:44
  So
• 16:45
  when
• 16:45
  it's
• 16:45
  really
• 16:45
  cold
• 16:45
  at
• 16:45
  night,
• 16:46
  it's
• 16:46
  hard,
• 16:47
  it's
• 16:47
  hard
• 16:47
  to
• 16:47
  find
• 16:47
  birds
• 16:48
  in
• 16:48
  the
• 16:48
  dark.
• 16:49
  And
• 16:49
  we
• 16:49
  don't
• 16:49
  really
• 16:50
  know
• 16:50
  where
• 16:50
  a
• 16:50
  lot
• 16:50
  of
• 16:50
  birds
• 16:51
  spend
• 16:51
  their
• 16:51
  time.
• 16:51
  So
• 16:51
  there
• 16:51
  have
• 16:52
  been
• 16:52
  some
• 16:52
  studies
• 16:54
  showing
• 16:54
  that,
• 16:54
  like
• 16:55
  kinglets,
• 16:55
  which
• 16:56
  are
• 16:56
  our
• 16:56
  tiniest
• 16:58
  winter
• 16:58
  bird
• 16:59
  here
• 16:59
  in
• 16:59
  North
• 16:59
  America,
• 17:01
  they
• 17:01
  can
• 17:01
  overwinter
• 17:02
  at
• 17:02
  really
• 17:02
  cold
• 17:03
  temperatures
• 17:03
  and
• 17:03
  they'll
• 17:04
  often
• 17:04
  huddle
• 17:05
  together
• 17:05
  to
• 17:05
  stay
• 17:06
  warm
• 17:06
  at
• 17:06
  night,
• 17:07
  which
• 17:07
  must
• 17:07
  be
• 17:07
  adorable
• 17:08
  if
• 17:08
  you
• 17:08
  like
• 17:09
  a
• 17:09
  little
• 17:10
  ball
• 17:10
  of
• 17:10
  golden
• 17:11
  crowned
• 17:11
  kinglets.
• 17:13
  And
• 17:14
  then
• 17:14
  there
• 17:14
  are
• 17:14
  some
• 17:14
  birds
• 17:15
  that
• 17:15
  make
• 17:15
  snow
• 17:16
  caves.
• 17:17
  So
• 17:17
  things
• 17:17
  like
• 17:17
  ruffed
• 17:18
  grouse
• 17:18
  and
• 17:18
  ptarmigan
• 17:19
  will
• 17:20
  dig
• 17:20
  this
• 17:21
  little
• 17:21
  cave
• 17:22
  in
• 17:22
  the
• 17:22
  snow.
• 17:23
  And
• 17:23
  when
• 17:24
  they're
• 17:24
  in
• 17:24
  the
• 17:24
  snow,
• 17:24
  then
• 17:25
  it
• 17:25
  can
• 17:25
  actually
• 17:25
  be
• 17:25
  warmer
• 17:26
  than
• 17:26
  it
• 17:26
  would
• 17:26
  be
• 17:27
  in
• 17:27
  the
• 17:28
  outside
• 17:28
  temperatures.
• 17:30
  And
• 17:30
  they're
• 17:31
  not
• 17:31
  the
• 17:31
  only
• 17:31
  ones.
• 17:32
  So
• 17:32
  red
• 17:32
  bulls
• 17:33
  can
• 17:33
  also
• 17:33
  do
• 17:33
  this,
• 17:34
  they'll
• 17:34
  dig
• 17:34
  these
• 17:34
  little
• 17:35
  tunnels
• 17:36
  and
• 17:36
  they
• 17:36
  can
• 17:36
  be
• 17:36
  kind
• 17:36
  of
• 17:37
  long
• 17:37
  and
• 17:38
  that
• 17:38
  helps
• 17:38
  protect
• 17:39
  them.
• 17:39
  And
• 17:39
  so
• 17:39
  I've
• 17:39
  always
• 17:40
  wondered,
• 17:40
  like,
• 17:40
  where
• 17:41
  are
• 17:41
  the
• 17:41
  juncos
• 17:42
  at
• 17:42
  night?
• 17:42
  Are
• 17:42
  they
• 17:42
  just
• 17:43
  like
• 17:43
  roosting
• 17:43
  in
• 17:43
  a
• 17:43
  bush
• 17:44
  together
• 17:44
  or
• 17:45
  where
• 17:45
  are
• 17:46
  they?
• 17:46
  And
• 17:46
  I
• 17:46
  have
• 17:46
  no
• 17:47
  idea.
• 17:47
  Yeah,
• 17:48
  well,
• 17:48
  yeah,
• 17:48
  if
• 17:48
  anyone
• 17:49
  is
• 17:49
  listening
• 17:49
  and
• 17:49
  has
• 17:49
  ever
• 17:50
  seen
• 17:50
  juncos
• 17:51
  at
• 17:51
  night,
• 17:51
  let
• 17:51
  us
• 17:51
  know.
• 17:52
  I
• 17:52
  mean,
• 17:52
  the
• 17:52
  chickadees
• 17:53
  that
• 17:53
  we
• 17:53
  study,
• 17:53
  sometimes,
• 17:54
  like
• 17:54
  when
• 17:54
  you
• 17:54
  go
• 17:55
  to
• 17:55
  check
• 17:55
  nest
• 17:55
  boxes
• 17:56
  and
• 17:56
  clean
• 17:56
  nest
• 17:56
  boxes,
• 17:57
  you
• 17:57
  can
• 17:57
  either
• 17:57
  find
• 17:58
  them
• 17:58
  in
• 17:58
  there
• 17:58
  roosting
• 17:59
  together
• 17:59
  or
• 18:00
  see
• 18:00
  the
• 18:00
  evidence
• 18:00
  that
• 18:01
  they
• 18:01
  were
• 18:01
  roosting,
• 18:01
  which
• 18:02
  is
• 18:02
  like
• 18:02
  their
• 18:03
  poops,
• 18:03
  which
• 18:03
  is
• 18:03
  pretty
• 18:03
  cute.
• 18:05
  Yeah.
• 18:05
  When
• 18:05
  I
• 18:05
  used
• 18:06
  to
• 18:06
  study
• 18:06
  tree
• 18:06
  swallows,
• 18:07
  same
• 18:07
  thing.
• 18:07
  Like
• 18:07
  on
• 18:08
  a
• 18:08
  cold
• 18:08
  night,
• 18:08
  you
• 18:08
  would
• 18:09
  find
• 18:09
  multiple
• 18:10
  individuals
• 18:11
  together
• 18:11
  sometimes.
• 18:12
  Yeah.
• 18:12
  I
• 18:12
  guess
• 18:12
  that
• 18:12
  brings
• 18:13
  up
• 18:13
  the
• 18:13
  broader
• 18:13
  question
• 18:13
  that,
• 18:14
  like,
• 18:14
  you
• 18:14
  know,
• 18:15
  these
• 18:15
  are
• 18:15
  birds
• 18:15
  that
• 18:15
  have
• 18:16
  evolved
• 18:16
  in
• 18:16
  some
• 18:16
  places
• 18:17
  or
• 18:17
  locally
• 18:17
  adapted
• 18:18
  in
• 18:18
  some
• 18:18
  places
• 18:19
  to
• 18:19
  be
• 18:19
  good
• 18:19
  at
• 18:20
  flexibly
• 18:21
  adjusting
• 18:21
  to
• 18:21
  their
• 18:22
  environment.
• 18:22
  And
• 18:22
  in
• 18:22
  other
• 18:23
  places
• 18:23
  where
• 18:23
  the
• 18:23
  environment
• 18:23
  isn't
• 18:24
  as
• 18:24
  variable,
• 18:25
  they
• 18:25
  have
• 18:25
  less
• 18:25
  of
• 18:25
  that
• 18:25
  ability.
• 18:26
  But
• 18:27
  kind
• 18:27
  of
• 18:27
  predictions
• 18:28
  are
• 18:28
  that
• 18:28
  variability
• 18:29
  is
• 18:29
  going
• 18:29
  up.
• 18:29
  Right.
• 18:30
  So,
• 18:30
  like,
• 18:31
  how
• 18:31
  do
• 18:31
  you
• 18:31
  think
• 18:31
  about
• 18:32
  that
• 18:32
  in
• 18:32
  the
• 18:32
  context?
• 18:32
  I
• 18:33
  mean,
• 18:33
  we
• 18:33
  can
• 18:33
  talk
• 18:33
  about
• 18:33
  juncos,
• 18:34
  but
• 18:34
  I
• 18:34
  know
• 18:34
  you've
• 18:34
  worked
• 18:34
  on
• 18:34
  other
• 18:34
  birds
• 18:35
  as
• 18:35
  well.
• 18:35
  This
• 18:36
  less
• 18:36
  predictable
• 18:37
  winter,
• 18:37
  what
• 18:38
  that's
• 18:38
  going
• 18:38
  to
• 18:38
  do
• 18:38
  to
• 18:38
  some
• 18:39
  of
• 18:39
  these
• 18:39
  patterns
• 18:39
  you've
• 18:39
  been
• 18:40
  finding.
• 18:40
  Yeah,
• 18:41
  So
• 18:42
  I
• 18:42
  think
• 18:42
  it's.
• 18:43
  I
• 18:43
  think
• 18:43
  some
• 18:44
  birds
• 18:44
  are
• 18:44
  going
• 18:44
  to
• 18:44
  fare
• 18:45
  better
• 18:45
  than
• 18:45
  others.
• 18:45
  So.
• 18:46
  So
• 18:46
  I
• 18:46
  think.
• 18:47
  I
• 18:47
  actually
• 18:47
  think
• 18:48
  juncos
• 18:48
  are
• 18:48
  going
• 18:48
  to
• 18:48
  be
• 18:49
  just
• 18:49
  fine
• 18:50
  because
• 18:50
  I
• 18:50
  think
• 18:50
  they're
• 18:50
  really
• 18:50
  good
• 18:51
  at
• 18:51
  responding
• 18:51
  to
• 18:51
  these
• 18:52
  temperature
• 18:52
  changes.
• 18:53
  But
• 18:53
  other
• 18:53
  birds
• 18:54
  that
• 18:54
  don't
• 18:55
  experience
• 18:55
  a
• 18:56
  lot
• 18:56
  of
• 18:56
  variation
• 18:56
  in
• 18:56
  temperature,
• 18:57
  I
• 18:57
  think
• 18:57
  are
• 18:57
  going
• 18:58
  to
• 18:58
  have
• 18:58
  a
• 18:58
  harder
• 18:58
  time
• 18:58
  dealing
• 18:59
  with
• 18:59
  some
• 18:59
  of
• 19:00
  these
• 19:01
  weather
• 19:01
  events
• 19:02
  that
• 19:02
  we're
• 19:02
  experiencing.
• 19:03
  And
• 19:03
  so
• 19:03
  I
• 19:04
  think
• 19:04
  a
• 19:04
  really
• 19:04
  good
• 19:04
  example
• 19:05
  of
• 19:05
  that
• 19:05
  are
• 19:06
  the
• 19:06
  polar
• 19:06
  vortices
• 19:07
  that
• 19:08
  we've
• 19:08
  been
• 19:08
  experiencing
• 19:09
  in
• 19:09
  North
• 19:09
  America.
• 19:10
  So
• 19:10
  this
• 19:10
  is
• 19:11
  where
• 19:11
  this
• 19:11
  really
• 19:11
  cold
• 19:12
  arctic
• 19:12
  air
• 19:12
  comes
• 19:13
  down
• 19:14
  and
• 19:14
  it
• 19:15
  can
• 19:15
  dip
• 19:15
  pretty
• 19:15
  low
• 19:16
  into
• 19:16
  the
• 19:16
  lower
• 19:17
  48
• 19:17
  in
• 19:18
  places
• 19:18
  that
• 19:18
  often
• 19:19
  don't
• 19:19
  receive
• 19:20
  these
• 19:20
  cold
• 19:21
  temperatures.
• 19:21
  And
• 19:22
  so
• 19:22
  this
• 19:22
  happened
• 19:23
  this
• 19:23
  winter,
• 19:25
  but
• 19:25
  it
• 19:25
  also
• 19:25
  happened
• 19:26
  a
• 19:26
  few
• 19:26
  years
• 19:26
  ago
• 19:26
  when
• 19:27
  there
• 19:27
  was
• 19:27
  that
• 19:28
  great
• 19:28
  Texas
• 19:29
  freeze.
• 19:30
  And
• 19:31
  you'll
• 19:31
  remember,
• 19:32
  like
• 19:32
  the
• 19:33
  news
• 19:33
  and
• 19:33
  social
• 19:33
  media
• 19:34
  was
• 19:34
  just
• 19:35
  inundated
• 19:36
  with
• 19:36
  pictures
• 19:37
  of
• 19:37
  Texas
• 19:38
  and
• 19:38
  Louisiana,
• 19:39
  that
• 19:39
  Gulf
• 19:39
  coast
• 19:40
  region
• 19:40
  covered
• 19:41
  in
• 19:41
  ice,
• 19:42
  people
• 19:42
  without
• 19:42
  power,
• 19:43
  huge
• 19:44
  crop
• 19:44
  destruction
• 19:45
  and
• 19:45
  livestock
• 19:46
  destruction.
• 19:47
  And
• 19:47
  a
• 19:47
  lot
• 19:47
  of
• 19:48
  birds
• 19:48
  also
• 19:48
  died
• 19:49
  during
• 19:49
  that
• 19:49
  event.
• 19:51
  So
• 19:51
  we
• 19:51
  found
• 19:52
  that
• 19:52
  purple
• 19:53
  martins,
• 19:54
  which
• 19:55
  are
• 19:55
  a
• 19:56
  breeder
• 19:56
  across
• 19:57
  North
• 19:58
  America,
• 19:59
  they
• 19:59
  overwinter
• 20:00
  in
• 20:00
  Brazil
• 20:01
  and
• 20:01
  then
• 20:01
  they
• 20:01
  come
• 20:02
  back
• 20:02
  to
• 20:02
  the
• 20:02
  breeding
• 20:03
  grounds
• 20:03
  fairly
• 20:04
  early
• 20:04
  in
• 20:04
  that
• 20:04
  area.
• 20:05
  So
• 20:05
  in
• 20:05
  the
• 20:05
  Gulf
• 20:05
  coast
• 20:06
  region,
• 20:07
  they'll
• 20:07
  get
• 20:07
  back
• 20:07
  in
• 20:08
  January
• 20:08
  or
• 20:09
  early
• 20:09
  February
• 20:10
  and
• 20:10
  set
• 20:10
  up
• 20:11
  shop.
• 20:12
  And
• 20:12
  they
• 20:12
  mostly
• 20:12
  make
• 20:13
  use
• 20:13
  of
• 20:14
  human
• 20:15
  provided
• 20:15
  houses.
• 20:16
  So
• 20:16
  you
• 20:16
  might
• 20:17
  have
• 20:17
  seen
• 20:17
  these
• 20:17
  big
• 20:18
  white
• 20:18
  gourds
• 20:18
  and
• 20:19
  nest
• 20:19
  boxes.
• 20:20
  And
• 20:20
  they
• 20:20
  nest
• 20:21
  often
• 20:21
  in
• 20:22
  these
• 20:22
  communal
• 20:23
  groups,
• 20:24
  so
• 20:24
  you'll
• 20:24
  see
• 20:24
  many
• 20:24
  of
• 20:25
  them
• 20:25
  together.
• 20:26
  And
• 20:26
  so
• 20:26
  all
• 20:26
  these
• 20:27
  birds
• 20:27
  had
• 20:27
  arrived
• 20:28
  back
• 20:29
  to
• 20:29
  Texas
• 20:30
  and
• 20:30
  Louisiana
• 20:31
  in
• 20:31
  January,
• 20:31
  and
• 20:32
  then
• 20:32
  this
• 20:33
  great
• 20:33
  Texas
• 20:33
  freeze
• 20:34
  hit
• 20:35
  in
• 20:36
  early
• 20:36
  February
• 20:36
  and
• 20:37
  it
• 20:37
  killed
• 20:37
  hundreds
• 20:38
  of
• 20:38
  purple
• 20:38
  martins.
• 20:39
  And
• 20:40
  we
• 20:40
  think
• 20:41
  that
• 20:41
  that's
• 20:41
  because
• 20:41
  they're
• 20:42
  just
• 20:42
  not
• 20:42
  used
• 20:43
  to
• 20:43
  these
• 20:43
  cold
• 20:43
  temperatures.
• 20:44
  They
• 20:44
  wouldn't
• 20:44
  ever
• 20:45
  experience
• 20:45
  them.
• 20:46
  So
• 20:46
  they
• 20:46
  usually
• 20:47
  avoid
• 20:47
  them
• 20:47
  by
• 20:47
  being
• 20:47
  in
• 20:48
  Brazil.
• 20:48
  And
• 20:48
  then
• 20:49
  by
• 20:49
  the
• 20:49
  time
• 20:49
  they
• 20:49
  get
• 20:49
  back,
• 20:49
  things
• 20:50
  are
• 20:50
  starting
• 20:50
  to
• 20:50
  warm
• 20:51
  up
• 20:51
  and
• 20:51
  so
• 20:52
  they
• 20:52
  don't
• 20:52
  ever
• 20:53
  get
• 20:53
  these
• 20:54
  winter
• 20:54
  storms.
• 20:55
  But
• 20:56
  with
• 20:56
  climate
• 20:56
  change,
• 20:57
  these
• 20:58
  polar
• 20:59
  vortices
• 20:59
  are
• 20:59
  bringing
• 21:00
  those
• 21:00
  storms
• 21:00
  in
• 21:00
  later
• 21:01
  in
• 21:01
  the
• 21:01
  season
• 21:01
  and
• 21:02
  they're
• 21:02
  hitting
• 21:02
  further
• 21:02
  south
• 21:03
  than
• 21:03
  they
• 21:03
  might
• 21:04
  otherwise
• 21:04
  have
• 21:04
  done.
• 21:05
  And
• 21:05
  so
• 21:05
  it
• 21:05
  can
• 21:05
  have
• 21:05
  really
• 21:07
  large
• 21:07
  consequences
• 21:08
  on
• 21:08
  these
• 21:09
  bird
• 21:09
  populations.
• 21:11
  Yeah,
• 21:11
  it
• 21:12
  makes
• 21:12
  sense
• 21:12
  that
• 21:12
  these
• 21:12
  birds
• 21:13
  that
• 21:13
  experience
• 21:13
  cold
• 21:14
  weather,
• 21:14
  like
• 21:14
  juncos,
• 21:15
  and
• 21:15
  experience
• 21:16
  variably
• 21:16
  cold
• 21:17
  weather
• 21:17
  across
• 21:17
  their
• 21:17
  whole
• 21:18
  range
• 21:18
  would
• 21:19
  have
• 21:19
  some
• 21:19
  ability
• 21:20
  to
• 21:20
  adapt
• 21:20
  and
• 21:20
  adjust
• 21:21
  to
• 21:21
  these.
• 21:21
  But
• 21:21
  yeah,
• 21:21
  for
• 21:21
  these
• 21:22
  aerial
• 21:22
  insectivores
• 21:23
  or
• 21:23
  tropical
• 21:23
  species
• 21:24
  that
• 21:24
  just
• 21:26
  in
• 21:26
  theory
• 21:26
  should
• 21:26
  be
• 21:27
  timing
• 21:27
  their
• 21:27
  life
• 21:28
  events
• 21:28
  to
• 21:29
  avoid
• 21:29
  a
• 21:29
  polar
• 21:30
  vortex
• 21:31
  wouldn't
• 21:31
  fare
• 21:32
  so
• 21:32
  well
• 21:32
  in,
• 21:32
  in
• 21:32
  the
• 21:33
  presence
• 21:33
  of
• 21:33
  one.
• 21:33
  And
• 21:33
  yeah,
• 21:34
  I
• 21:34
  guess
• 21:34
  my
• 21:34
  understanding
• 21:35
  of
• 21:35
  the
• 21:35
  polar
• 21:35
  vortex
• 21:36
  and
• 21:37
  its
• 21:37
  increasing
• 21:38
  frequency
• 21:38
  is
• 21:39
  the
• 21:39
  instability
• 21:39
  or
• 21:39
  increasing
• 21:40
  instability
• 21:40
  of
• 21:41
  the
• 21:41
  jet
• 21:41
  stream.
• 21:41
  Right.
• 21:42
  It
• 21:42
  allows
• 21:42
  this
• 21:43
  really
• 21:43
  cold
• 21:43
  Arctic
• 21:44
  air
• 21:44
  to
• 21:44
  blast
• 21:44
  south
• 21:46
  because
• 21:46
  the
• 21:47
  jet
• 21:47
  stream
• 21:47
  is
• 21:47
  weakening.
• 21:48
  I'm
• 21:48
  pretty
• 21:48
  sure.
• 21:48
  Yeah.
• 21:49
  And
• 21:49
  I.
• 21:49
  And
• 21:49
  that
• 21:50
  was
• 21:50
  a
• 21:50
  good
• 21:50
  point,
• 21:50
  that
• 21:52
  purple
• 21:52
  martins
• 21:53
  are
• 21:53
  aerial
• 21:53
  insectivores,
• 21:54
  meaning
• 21:54
  that
• 21:54
  they
• 21:55
  eat
• 21:56
  insects
• 21:57
  sort
• 21:57
  of
• 21:57
  exclusively.
• 21:58
  And
• 21:58
  so
• 21:58
  when
• 21:59
  it's
• 21:59
  really
• 21:59
  cold
• 22:01
  and
• 22:01
  snowing,
• 22:02
  there
• 22:02
  are
• 22:02
  not
• 22:03
  a
• 22:03
  lot
• 22:03
  of
• 22:03
  insects
• 22:03
  flying.
• 22:05
  And
• 22:05
  so
• 22:06
  it
• 22:06
  doesn't
• 22:06
  seem
• 22:07
  like
• 22:07
  something
• 22:07
  that
• 22:07
  they're
• 22:08
  going
• 22:08
  to
• 22:08
  be
• 22:08
  able
• 22:08
  to
• 22:08
  adapt
• 22:09
  to
• 22:09
  in
• 22:10
  the
• 22:10
  future.
• 22:10
  The
• 22:11
  insects
• 22:11
  just
• 22:11
  aren't
• 22:11
  going
• 22:12
  to
• 22:12
  be
• 22:12
  out,
• 22:12
  so
• 22:12
  they
• 22:12
  won't
• 22:13
  have
• 22:13
  any
• 22:13
  food.
• 22:13
  So
• 22:14
  I
• 22:14
  don't
• 22:14
  really
• 22:14
  see
• 22:14
  them
• 22:15
  overcoming
• 22:16
  this
• 22:16
  problem.
• 22:17
  No.
• 22:17
  Yeah,
• 22:18
  that
• 22:18
  makes
• 22:18
  sense.
• 22:18
  Especially
• 22:19
  like,
• 22:19
  even
• 22:19
  if
• 22:19
  they,
• 22:20
  even
• 22:20
  if
• 22:20
  they
• 22:20
  could
• 22:21
  shiver
• 22:21
  enough
• 22:21
  to
• 22:22
  stay
• 22:22
  warm,
• 22:22
  there's
• 22:22
  nothing
• 22:23
  to
• 22:23
  power
• 22:23
  the
• 22:23
  shivering
• 22:24
  because
• 22:24
  they're
• 22:24
  not
• 22:25
  gonna
• 22:25
  diet
• 22:26
  switch
• 22:26
  and
• 22:26
  just
• 22:27
  like
• 22:27
  show
• 22:27
  up
• 22:27
  at
• 22:27
  our
• 22:27
  feeders
• 22:28
  and
• 22:28
  eat
• 22:28
  seeds.
• 22:28
  Yeah.
• 22:29
  In
• 22:29
  the
• 22:29
  Northeast,
• 22:30
  where
• 22:30
  we.
• 22:30
  Well,
• 22:31
  we've
• 22:31
  had
• 22:31
  a
• 22:31
  really
• 22:31
  cold,
• 22:33
  snowy
• 22:33
  year.
• 22:34
  That
• 22:34
  hasn't
• 22:34
  been
• 22:35
  the
• 22:35
  case
• 22:35
  over
• 22:35
  the
• 22:35
  last
• 22:35
  few
• 22:36
  years,
• 22:36
  so
• 22:36
  we've
• 22:36
  been
• 22:36
  getting
• 22:38
  slightly
• 22:39
  warmer,
• 22:39
  but
• 22:40
  wet
• 22:40
  winters,
• 22:41
  so
• 22:42
  It'll
• 22:42
  be
• 22:42
  like
• 22:43
  40
• 22:43
  and
• 22:43
  raining.
• 22:45
  And
• 22:45
  I
• 22:45
  think
• 22:45
  that
• 22:45
  also
• 22:46
  has
• 22:46
  consequences
• 22:47
  for
• 22:47
  the
• 22:47
  birds.
• 22:48
  So
• 22:48
  the
• 22:48
  feathers,
• 22:49
  the
• 22:49
  insulation
• 22:49
  that
• 22:50
  we
• 22:50
  were
• 22:50
  talking
• 22:50
  about
• 22:51
  works
• 22:51
  best
• 22:52
  when
• 22:52
  those
• 22:52
  feathers
• 22:53
  are
• 22:53
  dry
• 22:53
  and
• 22:53
  they
• 22:53
  can
• 22:54
  stay
• 22:54
  nice
• 22:54
  and
• 22:54
  fluffy.
• 22:55
  So
• 22:55
  if
• 22:55
  it's
• 22:55
  raining
• 22:55
  all
• 22:56
  the
• 22:56
  time,
• 22:56
  that
• 22:57
  insulative
• 22:57
  property
• 22:58
  is
• 22:59
  not
• 22:59
  as
• 22:59
  effective.
• 23:00
  And
• 23:01
  so
• 23:02
  folks
• 23:02
  in
• 23:02
  my
• 23:02
  lab
• 23:02
  are
• 23:02
  also
• 23:03
  looking
• 23:03
  at
• 23:03
  how
• 23:04
  these
• 23:05
  warmer
• 23:05
  winters
• 23:06
  might
• 23:07
  influence
• 23:07
  energetics
• 23:08
  of
• 23:09
  our
• 23:09
  winter
• 23:09
  communities
• 23:09
  as
• 23:10
  well.
• 23:10
  Yeah,
• 23:10
  I
• 23:10
  mean,
• 23:11
  it's
• 23:11
  a
• 23:11
  very
• 23:11
  good
• 23:11
  point.
• 23:11
  You
• 23:11
  assume,
• 23:12
  okay,
• 23:12
  it's
• 23:12
  warmer,
• 23:13
  maybe
• 23:13
  they'll
• 23:13
  do
• 23:13
  better,
• 23:13
  but
• 23:13
  not
• 23:14
  if
• 23:14
  the
• 23:14
  insulin
• 23:15
  of
• 23:15
  the
• 23:15
  capacity
• 23:16
  of
• 23:16
  their
• 23:16
  feathers
• 23:16
  is
• 23:16
  also
• 23:17
  reduced.
• 23:17
  One
• 23:17
  thing
• 23:17
  I'd
• 23:18
  be
• 23:18
  really
• 23:18
  curious
• 23:19
  to
• 23:19
  hear
• 23:19
  more
• 23:19
  about
• 23:19
  is,
• 23:20
  you
• 23:20
  know,
• 23:20
  since
• 23:21
  you
• 23:21
  started
• 23:21
  your
• 23:22
  journey
• 23:22
  as
• 23:22
  a
• 23:22
  avian
• 23:23
  physiologist,
• 23:24
  thinking
• 23:24
  a
• 23:24
  lot
• 23:24
  about
• 23:25
  cold
• 23:25
  tolerance
• 23:25
  and
• 23:26
  adaptation
• 23:26
  to
• 23:27
  cold,
• 23:27
  what
• 23:27
  are
• 23:28
  some
• 23:28
  of
• 23:28
  the
• 23:28
  most
• 23:28
  exciting
• 23:29
  findings
• 23:29
  that
• 23:30
  have
• 23:30
  come
• 23:30
  out
• 23:30
  or
• 23:31
  what
• 23:31
  are
• 23:31
  you
• 23:31
  really
• 23:31
  excited
• 23:32
  about
• 23:32
  exploring?
• 23:33
  I
• 23:33
  think
• 23:33
  one
• 23:33
  of
• 23:34
  the
• 23:34
  most
• 23:34
  exciting
• 23:35
  things
• 23:36
  that
• 23:36
  have
• 23:36
  come
• 23:36
  out
• 23:36
  is
• 23:36
  just
• 23:37
  how
• 23:37
  low
• 23:37
  bird
• 23:38
  body
• 23:38
  temperatures
• 23:39
  can
• 23:39
  go.
• 23:40
  And
• 23:40
  so
• 23:40
  thinking
• 23:40
  back
• 23:41
  to
• 23:41
  torpor,
• 23:42
  which
• 23:42
  again
• 23:43
  is
• 23:43
  this
• 23:43
  state
• 23:44
  of
• 23:44
  inactivity
• 23:45
  that
• 23:45
  some
• 23:46
  birds
• 23:46
  can
• 23:46
  go
• 23:47
  into.
• 23:48
  And
• 23:49
  in
• 23:49
  this
• 23:49
  state
• 23:49
  they
• 23:49
  drop
• 23:50
  their
• 23:50
  body
• 23:50
  temperature,
• 23:50
  they
• 23:51
  drop
• 23:51
  their
• 23:51
  metabolic
• 23:52
  rate,
• 23:52
  they
• 23:52
  drop
• 23:52
  their
• 23:52
  heart
• 23:53
  rate.
• 23:54
  And
• 23:54
  there's
• 23:55
  been
• 23:55
  work
• 23:55
  done
• 23:56
  in
• 23:56
  Andean
• 23:57
  hummingbirds.
• 23:59
  So
• 23:59
  hummingbirds
• 24:00
  that
• 24:00
  exist
• 24:01
  at
• 24:02
  mid
• 24:02
  to
• 24:03
  high
• 24:03
  elevation
• 24:03
  in
• 24:04
  Peru,
• 24:05
  there's
• 24:05
  one
• 24:05
  species
• 24:06
  called,
• 24:06
  called
• 24:07
  the
• 24:07
  black
• 24:07
  metal
• 24:07
  tail.
• 24:08
  And
• 24:08
  it
• 24:08
  can
• 24:09
  drop
• 24:09
  its
• 24:09
  body
• 24:10
  temperature
• 24:11
  down
• 24:11
  to
• 24:11
  about
• 24:12
  3
• 24:12
  degrees
• 24:12
  Celsius,
• 24:13
  which
• 24:13
  is
• 24:13
  like,
• 24:14
  wow,
• 24:15
  38
• 24:15
  degrees
• 24:16
  Fahrenheit,
• 24:17
  which
• 24:17
  is
• 24:18
  cold.
• 24:19
  That's
• 24:19
  cold.
• 24:21
  Yeah.
• 24:21
  And
• 24:21
  so
• 24:21
  that's,
• 24:22
  that's
• 24:22
  the
• 24:22
  coldest
• 24:23
  that
• 24:23
  we
• 24:23
  know
• 24:24
  of
• 24:24
  a
• 24:24
  bird
• 24:24
  going,
• 24:26
  which
• 24:26
  is
• 24:26
  just
• 24:27
  mind
• 24:27
  boggling
• 24:27
  to
• 24:28
  me
• 24:28
  because
• 24:28
  I
• 24:29
  don't,
• 24:29
  I
• 24:29
  actually
• 24:30
  hate
• 24:30
  the
• 24:30
  cold.
• 24:31
  I
• 24:32
  think
• 24:32
  that's
• 24:32
  why,
• 24:33
  I
• 24:34
  think
• 24:34
  that's
• 24:34
  why
• 24:34
  I
• 24:35
  study
• 24:36
  whole
• 24:36
  adaptation
• 24:37
  in
• 24:37
  birds
• 24:37
  is
• 24:38
  because
• 24:38
  I'm
• 24:38
  just
• 24:38
  so
• 24:39
  fascinated
• 24:39
  by
• 24:40
  how
• 24:40
  they
• 24:40
  deal
• 24:40
  with
• 24:40
  it.
• 24:41
  And
• 24:41
  I
• 24:41
  like
• 24:41
  to
• 24:41
  watch
• 24:42
  them
• 24:42
  from
• 24:43
  inside
• 24:43
  the
• 24:43
  comfort
• 24:44
  of
• 24:44
  my
• 24:44
  warm
• 24:44
  home.
• 24:46
  And
• 24:48
  the
• 24:48
  idea
• 24:48
  that
• 24:49
  if
• 24:49
  I'm
• 24:50
  outside
• 24:50
  and
• 24:50
  it's
• 24:50
  38
• 24:51
  degrees
• 24:51
  Fahrenheit,
• 24:52
  I'm
• 24:52
  pretty
• 24:53
  uncomfortable.
• 24:54
  Just
• 24:55
  my
• 24:55
  feet,
• 24:55
  like
• 24:56
  you
• 24:56
  were
• 24:56
  saying,
• 24:56
  I
• 24:56
  don't
• 24:56
  have
• 24:57
  any
• 24:57
  blood
• 24:57
  flow
• 24:57
  down
• 24:57
  there.
• 24:58
  My
• 24:59
  face
• 24:59
  gets
• 24:59
  really
• 24:59
  cold.
• 25:00
  And
• 25:00
  the
• 25:00
  fact
• 25:00
  that
• 25:01
  birds
• 25:01
  could
• 25:01
  do
• 25:01
  that
• 25:01
  internally
• 25:03
  is
• 25:03
  mind
• 25:03
  boggling.
• 25:05
  Yeah,
• 25:05
  no,
• 25:05
  that's
• 25:05
  crazy.
• 25:07
  I
• 25:07
  should
• 25:07
  clarify.
• 25:08
  I
• 25:08
  like
• 25:08
  cold
• 25:09
  weather,
• 25:09
  but
• 25:09
  I
• 25:10
  like
• 25:10
  being
• 25:10
  prepared
• 25:10
  for
• 25:11
  it.
• 25:11
  So
• 25:12
  if
• 25:12
  I'm
• 25:12
  outside
• 25:13
  in
• 25:13
  the
• 25:13
  cold,
• 25:13
  I
• 25:13
  want
• 25:13
  to
• 25:14
  be
• 25:14
  warm,
• 25:14
  you
• 25:14
  know,
• 25:14
  with
• 25:14
  my
• 25:15
  parka
• 25:15
  or
• 25:16
  whatever.
• 25:16
  It's
• 25:17
  funny
• 25:17
  though,
• 25:17
  when
• 25:17
  I.
• 25:18
  Yeah,
• 25:19
  exactly,
• 25:19
  exactly.
• 25:20
  Very,
• 25:20
  very
• 25:20
  good
• 25:21
  insulation.
• 25:25
  So
• 25:25
  let's
• 25:26
  talk
• 25:26
  a
• 25:26
  little
• 25:26
  bit
• 25:26
  about
• 25:26
  some
• 25:26
  other
• 25:27
  strategies
• 25:27
  or
• 25:28
  behaviors
• 25:28
  for
• 25:28
  staying
• 25:28
  warm.
• 25:29
  We
• 25:29
  often
• 25:29
  see
• 25:29
  birds
• 25:29
  just
• 25:30
  standing
• 25:30
  on
• 25:30
  one
• 25:31
  leg,
• 25:31
  one,
• 25:31
  like,
• 25:32
  kind
• 25:32
  of
• 25:32
  tucked
• 25:32
  up
• 25:32
  into
• 25:32
  their
• 25:33
  feathers.
• 25:33
  The
• 25:33
  other
• 25:33
  one
• 25:33
  they're
• 25:34
  standing
• 25:34
  on
• 25:34
  can.
• 25:35
  Do
• 25:35
  we
• 25:35
  know
• 25:35
  anything
• 25:35
  about,
• 25:36
  like,
• 25:36
  whether
• 25:36
  that's
• 25:36
  something
• 25:37
  to
• 25:37
  do
• 25:37
  with
• 25:37
  staying
• 25:37
  warm?
• 25:38
  Yes,
• 25:38
  it
• 25:39
  is.
• 25:39
  So
• 25:39
  in
• 25:39
  the
• 25:39
  winter,
• 25:40
  I
• 25:40
  think
• 25:40
  birds
• 25:40
  definitely
• 25:41
  do
• 25:41
  that
• 25:41
  to
• 25:41
  stay
• 25:41
  warm,
• 25:42
  and
• 25:42
  you'll
• 25:42
  see
• 25:42
  them
• 25:42
  sort
• 25:43
  of
• 25:43
  sitting
• 25:43
  on
• 25:43
  their
• 25:43
  feet
• 25:44
  a
• 25:44
  lot
• 25:44
  more,
• 25:45
  which
• 25:46
  makes
• 25:46
  it
• 25:46
  really
• 25:46
  hard
• 25:47
  if
• 25:47
  you
• 25:47
  put
• 25:48
  bands
• 25:49
  on
• 25:49
  those
• 25:49
  birds
• 25:49
  so
• 25:50
  that
• 25:50
  you
• 25:50
  could
• 25:50
  tell
• 25:50
  which
• 25:50
  individual
• 25:51
  was
• 25:51
  which.
• 25:52
  They
• 25:52
  love
• 25:52
  to
• 25:52
  sit
• 25:52
  on
• 25:53
  their
• 25:53
  feet
• 25:53
  when
• 25:53
  it's
• 25:53
  cold,
• 25:54
  so.
• 25:54
  So
• 25:54
  definitely
• 25:55
  tucking
• 25:55
  that
• 25:57
  foot
• 25:57
  up
• 25:57
  into
• 25:57
  their
• 25:58
  feathers
• 25:58
  helps
• 25:58
  to
• 25:58
  keep
• 25:58
  them
• 25:59
  warm.
• 25:59
  There's
• 25:59
  other
• 26:00
  things
• 26:00
  that
• 26:00
  they
• 26:00
  can
• 26:00
  do
• 26:01
  to
• 26:01
  reduce
• 26:01
  heat
• 26:01
  loss,
• 26:02
  too.
• 26:02
  So
• 26:03
  in
• 26:03
  addition
• 26:04
  to
• 26:04
  the
• 26:04
  countercurrent
• 26:05
  heat
• 26:05
  exchange,
• 26:05
  they
• 26:06
  might
• 26:06
  reduce
• 26:07
  blood
• 26:07
  flow
• 26:07
  to
• 26:07
  certain
• 26:07
  areas.
• 26:09
  We
• 26:09
  can
• 26:09
  do
• 26:09
  this
• 26:10
  too,
• 26:10
  right?
• 26:10
  Like,
• 26:10
  if
• 26:10
  it's
• 26:11
  really
• 26:12
  cold
• 26:12
  out,
• 26:13
  then
• 26:13
  we
• 26:13
  tend
• 26:14
  to
• 26:14
  have
• 26:14
  less
• 26:14
  blood
• 26:14
  flow
• 26:15
  to
• 26:15
  the
• 26:16
  surface
• 26:16
  of
• 26:16
  our
• 26:16
  skin.
• 26:16
  Whereas
• 26:17
  if
• 26:17
  it's
• 26:17
  really
• 26:17
  warm
• 26:18
  and
• 26:18
  we're,
• 26:18
  like,
• 26:18
  exercising,
• 26:19
  we
• 26:19
  want
• 26:19
  to
• 26:19
  shed
• 26:19
  that
• 26:20
  heat.
• 26:20
  We
• 26:20
  can
• 26:21
  increase
• 26:22
  the
• 26:22
  size
• 26:22
  of
• 26:23
  those
• 26:23
  capillaries
• 26:23
  and
• 26:23
  shed
• 26:24
  heat
• 26:24
  from
• 26:24
  our
• 26:25
  skin
• 26:25
  surface.
• 26:26
  So
• 26:26
  birds
• 26:26
  can
• 26:27
  do
• 26:27
  this
• 26:27
  too,
• 26:27
  and
• 26:27
  they
• 26:28
  tend
• 26:28
  to
• 26:28
  do
• 26:28
  it
• 26:28
  in
• 26:28
  the
• 26:28
  places
• 26:29
  that
• 26:29
  are
• 26:29
  exposed.
• 26:30
  So
• 26:30
  the
• 26:30
  bill
• 26:30
  is
• 26:31
  a
• 26:31
  great
• 26:31
  example.
• 26:32
  You
• 26:32
  don't
• 26:32
  really
• 26:32
  think
• 26:33
  of
• 26:33
  a
• 26:33
  lot
• 26:33
  of
• 26:33
  blood
• 26:33
  vessels
• 26:34
  being
• 26:34
  in
• 26:34
  the
• 26:34
  bill,
• 26:35
  but
• 26:35
  there
• 26:35
  are
• 26:36
  some.
• 26:36
  And
• 26:36
  so
• 26:36
  in
• 26:37
  the
• 26:37
  cold,
• 26:37
  they
• 26:37
  might
• 26:37
  close
• 26:38
  those
• 26:38
  blood
• 26:38
  vessels.
• 26:39
  Same
• 26:39
  thing
• 26:40
  with
• 26:40
  other
• 26:40
  exposed
• 26:41
  skin,
• 26:41
  like
• 26:41
  around
• 26:42
  the
• 26:42
  eye
• 26:43
  or
• 26:43
  any
• 26:44
  place
• 26:44
  they
• 26:44
  have
• 26:44
  exposed
• 26:45
  skin.
• 26:45
  Yeah.
• 26:45
  I
• 26:46
  think
• 26:46
  most
• 26:46
  people
• 26:46
  probably
• 26:47
  have
• 26:47
  never
• 26:47
  thought
• 26:47
  about
• 26:48
  the
• 26:48
  fact
• 26:48
  that
• 26:48
  there
• 26:48
  are
• 26:48
  blood
• 26:48
  vessels
• 26:49
  in
• 26:49
  a
• 26:49
  bird's
• 26:49
  body,
• 26:50
  because
• 26:50
  it
• 26:50
  seems
• 26:50
  like
• 26:50
  such
• 26:51
  a
• 26:52
  stationary.
• 26:53
  I
• 26:53
  think
• 26:53
  maybe
• 26:53
  people
• 26:53
  think
• 26:54
  about
• 26:54
  it
• 26:54
  like
• 26:54
  our
• 26:54
  fingernails
• 26:55
  or
• 26:55
  something
• 26:55
  like
• 26:56
  that,
• 26:56
  but
• 26:56
  it's
• 26:56
  a
• 26:56
  much
• 26:56
  more
• 26:57
  dynamic
• 26:58
  piece
• 26:58
  of
• 26:58
  a
• 26:59
  bird's
• 26:59
  body
• 26:59
  or
• 26:59
  part
• 27:00
  of
• 27:00
  a
• 27:00
  bird's
• 27:00
  body
• 27:00
  than
• 27:01
  we
• 27:01
  think.
• 27:01
  So
• 27:02
  it
• 27:02
  makes
• 27:02
  total
• 27:02
  sense
• 27:03
  that
• 27:03
  they'd
• 27:03
  shunt
• 27:04
  hot
• 27:04
  blood
• 27:04
  from
• 27:05
  going
• 27:05
  out
• 27:05
  to
• 27:05
  this
• 27:05
  thing
• 27:06
  that
• 27:06
  clearly
• 27:06
  cools
• 27:06
  down
• 27:07
  easily.
• 27:07
  It
• 27:07
  has
• 27:07
  no
• 27:07
  feathers
• 27:08
  on
• 27:08
  it,
• 27:08
  but
• 27:08
  I'd
• 27:08
  never
• 27:09
  really
• 27:09
  thought
• 27:09
  about
• 27:09
  that.
• 27:09
  A
• 27:10
  lot
• 27:10
  of
• 27:10
  our
• 27:10
  big
• 27:10
  owls,
• 27:11
  like
• 27:11
  snowy
• 27:11
  owls,
• 27:12
  you
• 27:13
  hear
• 27:13
  that
• 27:13
  they
• 27:13
  can
• 27:14
  survive
• 27:14
  temperatures
• 27:14
  down
• 27:14
  to
• 27:15
  negative
• 27:15
  80
• 27:15
  degrees
• 27:16
  Fahrenheit
• 27:17
  in
• 27:18
  the
• 27:18
  winter,
• 27:19
  which
• 27:19
  is
• 27:20
  cold.
• 27:21
  That's
• 27:21
  crazy.
• 27:22
  It's
• 27:22
  very
• 27:22
  cold.
• 27:22
  Really?
• 27:23
  That's
• 27:24
  what
• 27:24
  I
• 27:24
  read.
• 27:24
  I
• 27:24
  don't
• 27:25
  know
• 27:25
  who's
• 27:25
  out
• 27:25
  there
• 27:25
  measuring
• 27:26
  the
• 27:26
  temperature
• 27:26
  when
• 27:27
  it's
• 27:27
  negative
• 27:27
  80.
• 27:27
  And,
• 27:28
  like
• 27:28
  bird
• 27:28
  watching,
• 27:29
  they're
• 27:29
  dead.
• 27:31
  But
• 27:32
  I
• 27:32
  also
• 27:32
  think
• 27:33
  that
• 27:33
  it's
• 27:34
  more
• 27:34
  impressive.
• 27:35
  Like,
• 27:35
  those
• 27:35
  are
• 27:35
  big
• 27:35
  birds,
• 27:36
  right?
• 27:37
  I
• 27:37
  think
• 27:37
  it's
• 27:37
  more
• 27:37
  impressive
• 27:38
  that
• 27:38
  little
• 27:38
  birds
• 27:39
  can
• 27:39
  do
• 27:39
  it.
• 27:40
  So
• 27:42
  if
• 27:42
  you
• 27:42
  just
• 27:42
  think
• 27:43
  about
• 27:43
  sort
• 27:43
  of
• 27:43
  the
• 27:43
  laws
• 27:44
  of
• 27:44
  thermodynamics.
• 27:45
  Larger
• 27:47
  animals,
• 27:47
  larger
• 27:48
  birds
• 27:48
  are
• 27:48
  going
• 27:48
  to
• 27:48
  lose
• 27:49
  heat
• 27:50
  at
• 27:50
  a
• 27:50
  slower
• 27:51
  rate
• 27:51
  than
• 27:51
  our
• 27:51
  small
• 27:52
  birds.
• 27:52
  It's
• 27:53
  just
• 27:53
  surface
• 27:53
  area
• 27:53
  and
• 27:54
  volume.
• 27:54
  And
• 27:54
  so
• 27:55
  small
• 27:55
  birds
• 27:56
  that
• 27:56
  can
• 27:56
  survive
• 27:57
  really
• 27:57
  cold
• 27:57
  temperatures
• 27:58
  are
• 27:58
  just
• 27:59
  really
• 27:59
  good
• 28:00
  at
• 28:00
  insulating
• 28:01
  and
• 28:01
  producing
• 28:02
  heat.
• 28:02
  And
• 28:02
  I
• 28:02
  think
• 28:02
  the
• 28:03
  Red
• 28:03
  Pole
• 28:03
  is
• 28:03
  another
• 28:04
  great
• 28:04
  example
• 28:04
  of
• 28:04
  that.
• 28:05
  So,
• 28:05
  yeah,
• 28:06
  they
• 28:07
  can
• 28:07
  withstand
• 28:08
  temperatures
• 28:08
  of
• 28:08
  negative
• 28:09
  60
• 28:09
  degrees
• 28:10
  Fahrenheit,
• 28:11
  which
• 28:11
  is
• 28:11
  still
• 28:12
  very
• 28:12
  cold.
• 28:13
  That's
• 28:13
  unpleasant.
• 28:14
  That's
• 28:14
  so
• 28:14
  cold.
• 28:15
  Yeah.
• 28:16
  And
• 28:16
  redpolls
• 28:17
  are
• 28:17
  tiny
• 28:17
  little
• 28:18
  birds
• 28:18
  that.
• 28:19
  Yeah,
• 28:20
  that's
• 28:20
  amazing.
• 28:20
  I
• 28:20
  was
• 28:21
  thinking
• 28:21
  about
• 28:21
  like
• 28:21
  these
• 28:22
  small
• 28:22
  arctic
• 28:22
  passerines
• 28:23
  that
• 28:23
  like
• 28:23
  you
• 28:24
  say
• 28:24
  they
• 28:24
  have
• 28:24
  the
• 28:24
  wrong
• 28:25
  surface
• 28:25
  area
• 28:25
  to
• 28:25
  body
• 28:26
  ratio
• 28:26
  to
• 28:26
  retain
• 28:27
  a
• 28:27
  lot
• 28:27
  of
• 28:27
  heat.
• 28:27
  So
• 28:28
  they've
• 28:28
  got
• 28:28
  to
• 28:28
  have
• 28:28
  all
• 28:28
  these
• 28:28
  strategies
• 28:29
  to
• 28:29
  really
• 28:30
  persist.
• 28:30
  But
• 28:30
  minus
• 28:31
  60
• 28:31
  Fahrenheit.
• 28:32
  Wow.
• 28:33
  Yeah.
• 28:33
  Again,
• 28:34
  who
• 28:34
  figured
• 28:34
  that
• 28:35
  out?
• 28:37
  Couldn't
• 28:37
  wanna
• 28:37
  do
• 28:37
  that
• 28:37
  field
• 28:38
  work.
• 28:38
  Fairbanks,
• 28:39
  Alaska.
• 28:39
  That's
• 28:39
  my
• 28:40
  guess.
• 28:40
  Yeah.
• 28:41
  So
• 28:41
  we
• 28:41
  reached
• 28:41
  the
• 28:41
  part
• 28:41
  of
• 28:42
  the
• 28:42
  show
• 28:42
  that
• 28:42
  we
• 28:42
  call
• 28:42
  that's
• 28:42
  BS
• 28:43
  or
• 28:43
  that's
• 28:43
  bird
• 28:43
  stuff,
• 28:44
  where
• 28:44
  we
• 28:44
  give
• 28:44
  our
• 28:44
  guests
• 28:45
  an
• 28:45
  opportunity
• 28:45
  to
• 28:45
  debunk
• 28:46
  a
• 28:46
  myth
• 28:46
  that
• 28:46
  ruffles
• 28:47
  their
• 28:47
  feathers.
• 28:47
  So
• 28:48
  Maria,
• 28:48
  what
• 28:48
  do
• 28:48
  you
• 28:49
  want
• 28:49
  to
• 28:49
  call
• 28:49
  BS
• 28:49
  on?
• 28:50
  Well,
• 28:50
  I
• 28:50
  guess
• 28:51
  I
• 28:52
  learned
• 28:52
  birds
• 28:52
  were
• 28:52
  warm
• 28:53
  blooded
• 28:53
  and
• 28:53
  that
• 28:53
  meant
• 28:54
  that
• 28:54
  they
• 28:54
  maintained
• 28:55
  a
• 28:55
  constant
• 28:55
  body
• 28:56
  temperature.
• 28:58
  And
• 28:58
  that's
• 28:58
  what
• 28:59
  we
• 28:59
  think
• 29:00
  we
• 29:00
  do
• 29:00
  as
• 29:00
  humans.
• 29:01
  Right.
• 29:01
  98.6
• 29:02
  degrees
• 29:02
  Fahrenheit.
• 29:03
  That's
• 29:03
  where
• 29:04
  we're
• 29:04
  staying.
• 29:05
  But
• 29:05
  the
• 29:06
  more
• 29:06
  we
• 29:06
  look,
• 29:06
  the
• 29:06
  more
• 29:06
  we
• 29:07
  find
• 29:07
  that
• 29:07
  birds
• 29:08
  are
• 29:08
  actually
• 29:08
  able
• 29:09
  to
• 29:09
  vary
• 29:09
  their
• 29:10
  body
• 29:10
  temperature.
• 29:10
  It's
• 29:11
  not
• 29:11
  just
• 29:11
  the
• 29:11
  ones
• 29:12
  that
• 29:12
  can
• 29:12
  drop
• 29:13
  down
• 29:13
  to
• 29:13
  3
• 29:14
  degrees
• 29:16
  and
• 29:16
  go
• 29:16
  into
• 29:16
  torpor.
• 29:17
  It
• 29:17
  seems
• 29:18
  like
• 29:18
  birds
• 29:19
  can
• 29:19
  both
• 29:20
  raise
• 29:20
  and
• 29:20
  lower
• 29:21
  their
• 29:21
  body
• 29:21
  temperature
• 29:22
  pretty
• 29:22
  frequently.
• 29:23
  So
• 29:23
  anytime
• 29:24
  they
• 29:24
  want
• 29:24
  to
• 29:24
  save
• 29:24
  energy,
• 29:25
  really,
• 29:26
  it
• 29:26
  can
• 29:26
  be
• 29:26
  used
• 29:27
  in
• 29:27
  that
• 29:27
  way.
• 29:27
  So
• 29:27
  just
• 29:28
  dropping
• 29:28
  their
• 29:28
  body
• 29:28
  temperature
• 29:29
  a
• 29:29
  few
• 29:29
  degrees
• 29:29
  could
• 29:30
  help
• 29:30
  them
• 29:30
  save
• 29:31
  energy
• 29:31
  in
• 29:31
  the
• 29:31
  cold.
• 29:32
  And
• 29:32
  similarly,
• 29:32
  when
• 29:33
  it's
• 29:33
  really
• 29:33
  warm
• 29:33
  out,
• 29:33
  they
• 29:34
  might
• 29:34
  raise
• 29:34
  their
• 29:34
  body
• 29:34
  temperature
• 29:35
  a
• 29:35
  couple
• 29:35
  degrees
• 29:36
  instead
• 29:36
  of
• 29:37
  wasting
• 29:37
  energy
• 29:38
  shedding
• 29:38
  heat.
• 29:39
  Ah,
• 29:40
  cool.
• 29:40
  Yeah,
• 29:41
  that's,
• 29:41
  that's
• 29:41
  an
• 29:41
  awesome
• 29:42
  bs.
• 29:42
  I
• 29:42
  mean,
• 29:42
  I
• 29:42
  think
• 29:42
  we
• 29:43
  hear
• 29:43
  these
• 29:43
  terms
• 29:43
  warm
• 29:44
  blooded
• 29:44
  and
• 29:44
  cold
• 29:44
  blooded
• 29:45
  and
• 29:45
  they're,
• 29:45
  they're
• 29:46
  too
• 29:46
  generalized
• 29:47
  for
• 29:47
  sure.
• 29:47
  Since
• 29:47
  like,
• 29:48
  yeah,
• 29:48
  a
• 29:48
  turtle
• 29:48
  in
• 29:48
  the
• 29:49
  sun
• 29:49
  has
• 29:49
  a
• 29:49
  warmer
• 29:50
  body
• 29:50
  temperature
• 29:50
  than
• 29:50
  you
• 29:51
  or
• 29:51
  I
• 29:51
  do.
• 29:51
  And
• 29:51
  a,
• 29:51
  a
• 29:52
  bird
• 29:52
  in
• 29:52
  the
• 29:52
  cold
• 29:53
  might
• 29:53
  lower
• 29:53
  their
• 29:53
  body
• 29:54
  temperature.
• 29:54
  I
• 29:54
  love
• 29:54
  that.
• 29:55
  Great.
• 29:55
  Well,
• 29:55
  thanks
• 29:56
  so
• 29:56
  much
• 29:56
  for
• 29:56
  joining
• 29:56
  us.
• 29:56
  It's
• 29:57
  been
• 29:57
  really
• 29:57
  awesome
• 29:57
  to
• 29:57
  chat
• 29:58
  with
• 29:58
  you
• 29:58
  today
• 29:58
  and
• 29:58
  I
• 29:58
  appreciate
• 29:59
  you
• 29:59
  taking
• 29:59
  the
• 29:59
  time.
• 29:59
  Thanks
• 30:00
  for
• 30:00
  having
• 30:00
  me,
• 30:00
  Scott.
• 30:05
  Birds
• 30:05
  are
• 30:05
  dinosaurs
• 30:06
  and
• 30:06
  around
• 30:06
  here
• 30:06
  we
• 30:06
  like
• 30:06
  our
• 30:07
  snacks.
• 30:07
  So
• 30:07
  we
• 30:07
  end
• 30:07
  each
• 30:07
  episode
• 30:08
  with
• 30:08
  a
• 30:08
  dinosaur
• 30:08
  nugget.
• 30:09
  Today's
• 30:09
  nugget
• 30:10
  is
• 30:10
  birds
• 30:10
  are
• 30:11
  remarkably
• 30:11
  flexible
• 30:12
  winter
• 30:12
  athletes.
• 30:13
  They
• 30:13
  don't
• 30:13
  just
• 30:13
  rely
• 30:13
  on
• 30:14
  feathers.
• 30:14
  They
• 30:14
  dynamically
• 30:15
  adjust
• 30:15
  their
• 30:15
  behavior,
• 30:16
  muscles,
• 30:17
  metabolism,
• 30:18
  gastrointestinal
• 30:19
  system,
• 30:19
  and
• 30:19
  even
• 30:19
  body
• 30:20
  temperature
• 30:20
  to
• 30:20
  survive
• 30:21
  the
• 30:21
  cold,
• 30:21
  constantly
• 30:22
  fine
• 30:22
  tuning
• 30:23
  their
• 30:23
  physiology
• 30:23
  as
• 30:24
  conditions
• 30:24
  change.
• 30:25
  That's
• 30:26
  a
• 30:26
  wrap
• 30:26
  on
• 30:26
  this
• 30:26
  week's
• 30:26
  episode.
• 30:27
  Okay,
• 30:27
  but
• 30:27
  how
• 30:27
  do
• 30:27
  birds
• 30:28
  stay
• 30:28
  warm?
• 30:29
  If
• 30:29
  you
• 30:29
  like
• 30:29
  this
• 30:29
  episode,
• 30:30
  leave
• 30:30
  a
• 30:30
  comment
• 30:30
  like
• 30:30
  follow
• 30:31
  and
• 30:31
  subscribe.
• 30:31
  We'll
• 30:32
  catch
• 30:32
  you
• 30:32
  next
• 30:32
  time.
• 30:33
  Byeeee.
• 30:38
  Okay,
• 30:38
  But...
• 30:39
  Birds
• 30:39
  is
• 30:39
  hosted
• 30:40
  by
• 30:40
  Scott
• 30:40
  Taylor
• 30:41
  with
• 30:41
  production
• 30:42
  and
• 30:42
  creative
• 30:42
  by
• 30:43
  Zach
• 30:43
  Karl.