Category Archives: Bird Anatomy

Flapping Saves Energy

Bird Anatomy, Crows & Ravens
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 Phys.org, 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 Phys.org)

Birds Can Smell

Bird Anatomy
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?

Bird Anatomy
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

Bird Anatomy, Peregrines
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)

29 June 2017

Many birds molt once a year during summer’s “down time” between raising their young and fall migration.  At this point their feathers have worn out.

Shown here are four primary feathers (remiges) molted by a black-legged kittiwake.  It’s easy to see that these feathers are no longer in good shape for flight.  Their edges are ragged.

Notice how the white barbs are in worse shape than the black ones.  That’s because pigment adds strength to the feather.  The darker the pigment, the stronger the feather.  For this reason many sea birds have black tips on their white flight feathers and some birds have completely black primary and secondary feathers.

Adult peregrines molt once a year but it takes a long time. According to Birds of the World, resident peregrines in mid-latitude temperate zones (i.e. Pittsburgh) begin their molt in April and finish in September. The process takes 4.5 to 5 months to change out every feather but males and females don’t molt on the same schedule.

Peregrine falcon tail feather (photo from Shutterstock in 2013)

Male peregrines have to be in top hunting condition from May through June while the young need food at the nest and are learning to hunt. Males avoid replacing key flight feathers during that time.

However (news to me!) female peregrines begin to molt during incubation. This is 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 feather in the nest box. 

Molted peregrine feather in the Cathedral of Learning nestbox, Sept 2022 (photo from the National Aviary falconcam at Univ of Pittsburgh)

Special Equipment For Warming Eggs

Bird Anatomy, Nesting & Courtship

Dori rolls the eggs just before she resumes incubation (photo from the National Aviary falconcam at Gulf Tower)
Dori rolls the eggs before she resumes incubation (photo from the National Aviary falconcam at Gulf Tower)

To become baby birds, eggs must be warmed to around 98.6 °F and remain at that temperature while the embryos develop.  Adult birds that incubate(*) have special equipment to accomplish this:  bare skin on the belly called a brood patch.

We don’t usually see the brood patch because surrounding feathers close over it to keep the adult warm.  When a bird comes back to its nest to incubate, it opens its belly feathers to lay its bare skin against the eggs.  You may have seen peregrines open their belly feathers by standing over the eggs and rocking side to side.

Click on the link below to see an American kestrel’s brood patch and learn about this important part of bird anatomy, the Brood Patch.

 

(*) p.s. In eagles and peregrines, both sexes incubate so both have brood patches but this isn’t the case with all birds.  In many duck species, only the female incubates so the males don’t have brood patches.

 

(photo from the National Aviary falconcam at Gulf Tower)

Birds Wearing Black-n-Gold

Bird Anatomy, Bird Behavior

Black and yellow birds who flock together in Western Panama (photo composite)
Black and yellow birds who flock together in Western Panama (photo composite)

On Throw Back Thursday:

These birds are wearing black-n-gold!

Just before the Steelers AFC Championship game in 2011 I explained why these black and yellow species tend to flock together.

This Sunday the Steelers are again in the AFC Championship.  What better time to revisit birds wearing black-n-gold.  Read on!

Wearing Black ‘N’ Gold

 

(composite photo credits, top left to right, then bottom left to right:
1. Slate-throated Whitestart: Corey Finger on 10000birds.com
2. Sooty-capped Bush Tanager: Wikipedia
3. Yellow-thighed Finch: Wikimedia Commons
4. Collared Whitestart: Jan Axel on janbirdingblog.blogspot.com
5. Silver-throated Tanager: Kent Fiala’s Website
6. Yellow-throated Brush Finch: Atrevido1 at Solo Aves on Flickr)

How Birds Keep The Arctic Cool

Bird Anatomy, Water and Shore

Little auks (Alle alle) at Svalbard breeding colony (photo from Wikimedia Commons)
Little auks (Alle alle) at Svalbard breeding colony (photo from Wikimedia Commons)

Here’s amazing news:  Seabird colonies help keep the Arctic cool.

Seabirds gather on Arctic islands to breed during the summer.  Thousands of them nest close together and produce a lot of guano (bird poop).

Atmospheric scientists studying the Arctic noticed summertime bursts of ammonia-based particulate.  These tiny particles cause clouds to form because they gather moisture as they move through the air.  The clouds reflect sunlight and keep the land and water cool.

Where does the ammonia come from?  It wafts off the guano at the seabird colonies.

These findings were published on 15 November 2016 in Nature Communications.   Read the summary here at Science Daily.

 

(photo of little auks, Alle alle, at breeding colony on Svalbard by Alastair Rae from London, UK via Wikimedia Commons. Click on the image to see the original)