Category Archives: Bird Anatomy

For Best Results Copy Birds

Thirty years ago Japanese trains had a problem. They could travel fast but they caused sonic booms.

The answer was the bullet train.  How did Japanese engineers develop it?  They learned from birds.

Watch this 6+ minute video from Vox + 99% Invisible to learn how birds showed the way and follow one woman's quest to teach engineers that Nature has the answers.  Our world can benefit from biomimicry.

For best results, copy birds.

 

Thank you to Holly Hickling for sharing this.  For more cool videos, follow Vox (news site) or 99% Invisible (city design updates) on Facebook.

(video from Vox on YouTube)

The Wax Eaters Are Back In Town

Yellow-rumped warbler in autumn (photo by Cris Hamilton)
Yellow-rumped warbler in autumn (photo by Cris Hamilton)

After most warblers have left for the winter, the yellow-rumped warblers come back to town.

Breeding across Canada and the northern U.S., yellow-rumped warblers (Setophaga coronata) spend the winter in North America as close to us as Ohio and eastern Pennsylvania, though not usually in our area.  In late fall they stop by in Pittsburgh.

Yellow-rumps don't have to leave for Central or South America because they have a unique talent. Their bodies can digest wax.  In winter they eat the waxy fruits of bayberry and juniper.  Since bayberry is also called wax myrtle, it gave our common subspecies its name:  the myrtle warbler.

On Throw Back Thursday, learn how yellow-rumped warblers get nutrition from wax in this vintage article:  Anatomy: Wax Eaters.

 

p.s. Notice that the warbler in the Wax Eaters article is wearing bright breeding plumage in black, white and yellow . Autumn yellow-rumps are dull brown with a faint vest and a broken white eye ring. The best clue to their identity is their yellow rump.

Yellow-rumped warbler showing its yellow rump (photo by Cris Hamilton)
Yellow-rumped warbler showing its yellow rump (photo by Cris Hamilton)

(photos by Cris Hamilton)

When Birds Lost Their Teeth

 Model of Archaeopteryx on display at Geneva natural history museum (image via Wikimedia Commons)
Model of Archaeopteryx on display at Geneva natural history museum (image via Wikimedia Commons**)

Birds have no teeth but that wasn't always the case. We know that they're descended from toothy theropod dinosaurs -- in fact birds are dinosaurs -- so when did they lose their teeth?

In 2014, genome sequencing studies led by Robert W. Meredith worked to determine whether several branches of birds' ancestry lost their teeth independently (convergent evolution) or whether all birds have a common ancestor that evolved a toothless beak.

The project did full genome sequencing on 48 birds species representing nearly all modern bird orders.  They then focused their study on six genes related to tooth enamel.  All six genes became non-functional in a common bird ancestor around 116 million years ago.  That's when birds lost their teeth.

Birds eat plenty of things that require chewing so how do they do it?  Read this 2010 blog post Anatomy: Where Are Their Teeth? to find out.

 

More information on the bird genome project is here in Science magazine.

(cropped image of Archaeopteryx model on display at Geneva natural history museum via Wikimedia Commons; click on the image to see the original.  **Note that this Archaeopteryx model has accurate teeth but has other inaccurate/disputed features as described on Wikimedia Commons: "Archaeopteryx had a more round shape of its wings, the primary feathers were attached to the second finger unlike here, and these colours are now known to be wrong.")

How Old Is That Peregrine?

Adult peregrine falcon in flight, Univ.of Pittsburgh, 2016 (photo by Peter Bell)
Adult peregrine falcon in flight, Univ.of Pittsburgh, 2016 (photo by Peter Bell)

Now's a good time to brush up on identifying peregrine falcons since they pass by hawk watches in October, especially on the coast.  When you identify a peregrine you can also tell how old it is because the plumage is different in each age group:  adult, juvenile, and sub-adult.

Plumage provides an exact age for two groups in October:  Juveniles are first year birds, 6 months old, that hatched last spring. Sub-adults are second year birds, 18 months old, with nearly complete adult plumage.

Adults -- two or more years old -- all have the same plumage.  Unfortunately you can't know an adult's exact age unless the bird is banded and you find out its provenance.

Here's what they look like:

Adult peregrines (2+ years old in October) have fresh plumage in charcoal gray and white.  The photo at top shows an adult male in flight.  The photo below is an adult female.  Adults have:

  • Solid dark charcoal helmet (head)
  • Dark charcoal malar stripes (on face)
  • Clean white or slightly rosy chest and throat
  • Horizontal charcoal+white stripes on belly and flanks
  • Gray back: Male's is pale blue-gray.  Female's is "muddy" gray.

Adult peregrine, Univ of Pittsburgh, 2017 (photo by Peter Bell)
Adult peregrine, Univ of Pittsburgh, 2017 (photo by Peter Bell)

 

Juvenile peregrines (6 months old in October) are the same size as adults but their colors are brown+cream.  Juveniles have:

  • Variable brown helmet with some cream-colored traces (head)
  • Brown malar stripes (on face)
  • Cream colored chest that's striped all the way up to the throat
  • Vertical brown+cream stripes on belly and flanks
  • Brown back.
  • (Bonus!) Juveniles have cream-colored tips on their tails, visible as the sun shines through them in flight.

Juvenile peregrine in flight, Univ of Pittsburgh, 2012 (photo by Peter Bell)
Juvenile peregrine in flight, Univ of Pittsburgh, 2012 (photo by Peter Bell)

Above, a juvenile in flight.  Below a juvenile shows off the vertical stripes on his chest and belly.  His variable brown helmet with "eyes on the back of his head" and horizontal cream-colored line at his crown.

Juvenile peregrine falcon, Univ. of Pittsburgh, 2016 (photo by Peter Bell)
Juvenile peregrine falcon, Univ. of Pittsburgh, 2016 (photo by Peter Bell)

 

Sub-adults are 18 months old with nearly complete adult plumage except for a few juvenile feathers.  They began to molt into adult plumage last spring at 10-12 months old.  By October their few juvenile feathers are hard to see without a photograph.  They are ready to breed next spring.

Below, an 18-month-old peregrine named Spirit is in rehab at Medina Raptor Center in the autumn of 2014.  You can see her back is mostly gray with just a few brown feathers.  Her head shows faint traces of the juvenile cream colors.

18-month-old peregrine falcon, Spirit, in rehab at Medina Raptor Center, Nov. 2015 (photo by Kate St.John)
18-month-old peregrine falcon, Spirit, in rehab at Medina Raptor Center, Nov. 2015 (photo by Kate St.John)

For a view of sub-adult plumage in the spring, see these photos taken in March 2016 of a 10-month-old Juvenile Peregrine Falcon Transitioning Into Adult Plumage.

For additional tips, see Ageing Peregrine Falcons in the Field by Alex Lamoreaux at Nemesis Bird.

 

(all photos taken at University of Pittsburgh by Peter Bell ... except for the peregrine on the glove, "Spirit" at Medina Raptor Center, photo by Kate St. John)

Fat in Winter, Thin in Summer

Northern cardinals in May and February (photos by Cris Hamilton)
Northern cardinals in May and February (photos by Cris Hamilton)

Why do birds look fat in winter and thin in the summer?  Have they lost weight?

No.  They're trying to stay cool.

Underneath their smooth outer feathers birds wear down coats all year long.  The down keeps them especially warm when they fluff it out to hold more heat next to the skin.  This fluffing makes them look fat on cold winter days.

When it's hot, they can't take off their down coats so they force hot air out of the down by compressing their outer feathers.  This makes them look thin.

The cardinal on the left, above, is not the thinnest one I've ever seen.  Cris Hamilton took his picture in May when the temperature was pleasant.  He'll look considerably thinner this month.

It's just another way that birds cope with heat.

 

p.s. We think of down as white but on a northern cardinal it's black.  Click here to see a northern cardinal's body feather, called a semi-plume, black at the root and red at the tip.

(photos by Cris Hamilton)

Birds’ Beaks Are Air Conditioners

Song sparrow singing (photo by Peter Bell)
Song sparrow singing (photo by Peter Bell)

How do birds cope with heat?  They have several obvious ways and at least one we can't see.

Like us, birds stand in the shade and bathe to cool off.  They also appear to pant -- actually gular fluttering -- but their hidden cooling method is a surprise. They use the nasal conchae (pronounced KONK eye) inside their beaks.

Nasal conchae are complex structures that moderate the temperature of inhaled air and reclaim water from exhaled air.  Birds that live in hot dry places would benefit from bigger, better conchae.

A study published in The Auk: Ornithological Advances in 2016 found just that.

Raymond Danner of UNC Wilmington and his colleagues used CT scans to display the internal beak structures of two subspecies of song sparrows. The specimens were collected in Delaware and Washington, DC.

Delaware and D.C. don't seem to have different climates, but a bird of the dunes copes with a hot dry micro-climate compared to one that nests in a wooded inland park.

Indeed, as reported in Science Daily, the CT scans showed that "the conchae of the dune-dwelling sparrows had a larger surface area and were situated farther out in the bill than those of their inland relatives."

Here's a dune-dwelling song sparrow beak with elaborate air conditioning structures.

CT scan shows nasal conchae inside the bill of a Song Sparrow (photo credit: E. Gulson-Castillo and E. Sibbald via Science Daily)
CT scan shows nasal conchae inside the bill of a Song Sparrow (photo credit: E. Gulson-Castillo and E. Sibbald via Science Daily)

This extra internal gear means the dune-based song sparrows (Melospiza melodia atlantica) have larger beaks than their inland cousins.

I'll admit I haven't noticed the slightly larger beaks of the beach birds.  Have you?

 

(photo by Peter Bell)

Flapping Saves Energy

Multiple wingtips vortices roll off the tips of a flying jackdaw's wings (photo credit: Aron Hejdström via Science Daily)
Multiple wingtips vortices roll off the tips of a flying jackdaw's wings (photo linked from viaScience Daily, credit: Aron Hejdström)

It doesn't make sense but if your wings are the right shape flapping saves energy.

Birds and airplanes must constantly overcome drag to stay aloft. One source of induced drag occurs during lift when swirls of air, called vortices, roll off the wingtips.  This small plane generates a huge wingtip vortex, forcing it to burn more fuel as it flies.

Wingtip vortex from an airplane (photo from NASA in the public domain on Wikimedia Commons)
Wingtip vortex from an airplane (photo from NASA in the public domain on Wikimedia Commons)

 

Large soaring birds, such as turkey vultures, reduce drag in two ways. Their wingtip feathers form slots that break the single vortex into smaller ones (small is good!), and they turn their wingtips up as they soar.

Turkey vulture (photo by Chuck Tague)
Turkey vulture (photo by Chuck Tague)

Southwest Airlines turns up its wingtips, too, to save fuel.

Wingtip on a jet, tip turned up to reduce wingtip vortex (photo from Wikimedia Commons)
Wingtip turned up to reduce wingtip vortex (photo from Wikimedia Commons)

 

But what about smaller birds that flap all the time?  Are they doomed to inefficient, labor-intensive flight?  A new study from Sweden says no.

Biologists at Lund University studied jackdaws (Corvus monedula), a corvid smaller than the American crow. Using mist and multiple cameras they found that the birds' slotted feathers, specifically designed for flapping flight, also break up the vortex into multiple swirls.  See them rolling off the wings in the study photo at top.

Now that we know slots are efficient for both flapping and soaring, what prompted their development? The study's authors "propose the hypothesis that slotted wings evolved initially to improve performance in powered (i.e. flapping) flight."

In fact, flapping saves so much energy that author Anders Hedenström suggests, "We could potentially build more efficient drones to fly with active wingbeats. Within a ten-year period, we could see drones which have the morphology of a jackdaw."

Read more about the study at Science Daily or the original paper here at The Royal Society.

 

(photo by Aron Hejdström linked from Science Daily)

Birds Can Smell

Danielle Whittaker, BEACON researcher, used dark-eyed juncos to demonstrate how songbirds use scent to attract mates. Credit: Photo courtesy of BEACON
Dark-eyed juncos in scent study (photo courtesy of BEACON)

True or False?

Birds have little or no sense of smell.  ... False!

Turkey vultures, seabirds, kiwis and parrots are known for their sense of smell.  And every time I turn around a new study finds more species with olfactory prowess.  As Audubon Magazine says, "In fact, every bird tested has passed the sniff test."

Back in 2011 Danielle Whittaker showed that the scent in preen oil varies among dark-eyed juncos. Those who smell the best, from a junco's point of view, attract more mates.  Yes, dark-eyed juncos can smell.

Read more in this vintage article: They Use Cologne

 

(Photo: courtesy of BEACON via Science Daily)

Where Are Birds’ Ears?

Barn owls, western Pennsylvania, July 2017 (photo by Anthony Bruno)
Barn owls, western Pennsylvania, July 2017 (photo by Anthony Bruno)

Birds hear really well -- especially barn owls -- but where are their ears?

This vintage article from July 2010 reveals where they are in Anatomy: Under The Feathers.

 

p.s. Did you know barn owls' ears are lopsided?
Their left ear is opening higher than their right one!  Learn more in A Ranger's Random Walks blog post from November 2014.

 

(photo of barn owls, July 2017, by Anthony Bruno)

Feathers Wear Out

Recently molted feathers of Black-legged Kittiwake (photo by Jymm in public domain on Wikimedia)
Recently molted feathers of a black-legged kittiwake (photo by Jymm in public domain on Wikimedia)

On Throw Back Thursday:

Many birds molt during summer's "down time" between raising their young and fall migration.  At this point their feathers have worn out.

However (news to me!) female peregrine falcons choose a different time of year.  They begin to molt during incubation, a convenient time to do it because they're temporarily sedentary and their mates supply their food.  That's why we sometimes see a peregrine primary feather in the nest box.  Who knew!

Read more about feather wear and molting in this vintage article: Feathers Wear Out

 

(photo from Wikimedia, in the public domain.  Click on the photo to see the original)