Category Archives: Bird Anatomy

Next on the Agenda: Molting

Canada goose molting in late June (photo from Wikimedia Commons)

13 June 2024

As soon as the breeding season is over adult birds molt to change out their old feathers. During this period many birds look ragged. We’ll see a few bald cardinals and blue jays who’ve molted all their head feathers at once. Peregrines will seem lazy while they molt in July and August. Canada geese won’t be able to fly.

This week at Duck Hollow I noticed that Canada geese are already molting. Their white rumps are showing, which indicates they’ve lost all their flight feathers.

Not-molting vs. molting appearance in Canada geese (photos from Wikimedia Commons)

At the end of this month Pitt’s peregrines will be molting too. We might see a peregrine feather on the falconcam.

Peregrine falcon tail feather (photo from Shutterstock in 2013)

Learn more about molting in this vintage article.

Quick Looks at Size and Behavior

White-throated sparrow and black-and-white warbler from Wikimedia, FaB Peregrine parent checking on the chick

10 May 2024

Maybe you’ve noticed that after watching warblers for a while, sparrows look huge. Gloria (@Lucent508) captured them side by side.

On Day 25 at the peregrine nest at Charing Cross Hospital in London (Fulham and Barnes), one of the chicks explored the nestbox ramp. He stumbled on the last step but enjoyed the outing nonetheless (the stumble is last photo though it actually happened first). At one point his mother looked at him as if to say, “Are you OK out there?”

Even though they are not “persons,” falconcams give us insight into the individual personalities of the peregrines on camera. This year the new unbanded female at the Wakefield Cathedral Peregrines nest (@WfldPeregrines) in Yorkshire, England has a habit never observed in the previous female: “Our previous female would never stay in the nest whilst the male fed the chicks.”

In the video below the female watches the male feed the chick. Sometimes he passes her a morsel of food which she swallows … or she feeds it to the chick. It’s not often that you see two peregrine parents feeding one chick.

(credits are in the captions and embeds)

Are Piebald Birds More Common Now?

Leucistic common grackle, Frick Park, 26 Oct 2023 (photo by Charity Kheshgi)

7 November 2023

Last month at Frick Park Charity Kheshgi and I saw at least three birds with unusual white feathers in their plumage, a condition that labels them “leucistic.”

Leucism refers to an abnormality in the deposition of pigment in feathers. There is some disagreement as to whether the condition is genetic or caused by pigment cells that were damaged during development. Whatever the cause, the condition can result in a reduction in all types of pigment, causing pale or muted colors on the entire bird. Or the condition can cause irregular patches of white, and birds with these white patches are sometimes described as “pied” or “piebald.”

Audubon Podcast: Why Is This Bird Half-White?

This common grackle had white feather patches on his head that were not uniform from side to side.

Leucistic common grackle, Frick Park, 26 Oct 2023 (photo by Charity Kheshgi)

The circle of white dashes around his eyes indicate his eyelashes are white. (Did you know birds’ eyelashes are modified feathers?)

Leucistic grackle zoomed in, white dashes around his eyes (photo by Charity Kheshgi)

In early October we saw a white-faced chipping sparrow …

Leucistic chipping sparrow — white face, Frick Park, 7 October 2023 (photo by Charity Kheshgi)

… and a leucistic American robin in the middle of the month.

Leucistic American robin, Frick Park, 18 Oct 2023 (photo by Charity Kheshgi)

It seems that leucism is more common in robins than in other species — or at any rate I see more of them. Here’s one that was photographed in Missouri.

Leucistic American robin, (photo by Andy Reago & Chrissy McClaren via Wikimedia Commons)

This leucistic male red-winged blackbird, also seen in Missouri, looks like a new species!

Leucistic male red-winged blackbird (photo by Andy Reago & Chrissy McClarren via Flickr Creative Commons license)

Leucistic birds are memorable but are they becoming more common? It seems so to me but I cannot find a scientific study that answers question.

Meanwhile, read more about unusual white feather conditions at Audubon News: Albinism and Leucism.

(photos by Charity Kheshgi and by Andy Reago & Chrissy McClarren via Flickr Creative Commons license. credits are in the captions)

Male & Female Don’t Look Alike — But We Can’t See It

Eurasian blue tit (photo from Wikimedia Commons)

29 October 2023

Though 70% of the songbirds in our field guides have sexes that look the same to us, this isn’t true from the birds’ point of view. Birds can see ultraviolet light (we cannot) and often have plumage differences in the ultraviolet range. With the invention of inexpensive UV viewing equipment, scientists looked at birds and were amazed at what they found. 90% of the species tested had differences between males and females under UV light. We humans just can’t see it.

Eurasian blue tits (Cyanistes caeruleus), shown at top, were one of the first wild birds examined in the ultraviolet range. Both sexes look alike … or do they?

Using a spectrophotometry probe to scan the feathers of wild-caught birds, Andersson and his colleagues discovered that blue tits themselves have no problem telling males from females: Males have a patch of feathers on the crown of the head that strongly reflects UV light; females do not.

NWF: True Colors: How Birds See the World

This marked up photo gives you an idea of how a male might look if only we could see UV.

Blue tit (from Wikimedia Commons); mark-up shows location of sexually dimorphic feathers on males

Both sexes of yellow-breasted chats (Icteria virens) look the same from afar, though in the hand the sexes can be distinguished (interior mouth color for instance). A 2004 study, Sexual dichromatism in the yellow-breasted chat, detected that the male’s throat has ultraviolet colors that make it much brighter than the female’s.

Yellow-breasted chat in Lancaster, PA (photo from Wikimedia Commons)

Here’s what it might look like if only we could see it.

Yellow-breasted chat (from Wikimedia); mark-up shows location of sexually dimorphic feathers on males

In 2002 scientists studied ultraviolet plumage in picui doves (Columbina picui) of South America. Males and females look much the same to our human eyes but are dimorphic in the UV range.

Picu dove, male cooing (photo from Wikimedia Commons)

A lady dove sees so much more!

Picu dove (from Wikimedia Commons); mark-up shows location of sexually dimorphic feathers on males

Apparently most birds are sexually dimorphic in ultraviolet including cedar waxwings, barn swallows, mockingbirds and western meadowlarks. According to True Colors: How Birds See The World, biologist Muir Eaton scanned the plumage of museum study skins of 139 songbird species in which males and females appear alike — but they aren’t alike under UV. He concluded, “To the birds themselves, males and females look quite different from one another.”

For more information see:

It’s amazing how much we humans are missing.

(credits are in the captions with links to the originals)

Look How He Can Move His Eyes!

Great-tailed grackle (photo from Wikimedia Commons)

22 October 2023

The great-tailed grackle (Quiscalus mexicanus), a close relative of our common grackle, is so numerous and annoying in Austin, Texas in the winter that there are always news stories about them. This interview with a grackle researcher revealed a very cool fact about great-tailed grackles that probably applies to our grackles as well.

Great-tailed grackles can move their eyes independently to keep watch in two different directions at the same time! Check out the video below.

video from KUAN on YouTube

Look how he can move his eyes!

(credits are in the captions; click on the captions to see the originals)

Do Blackpolls Sleep in Flight Over the Atlantic?

Blackpoll warbler in PA, Oct 2020 (photo from Wikimedia Commons)

5 October 2023

Some birds are champion fliers, staying airborne for days or months at a time. Scientists wondered if birds sleep in flight and proved that they do in a 2016 study of great frigatebirds, finding that the birds either “sleep with one half of their brains active, or with both hemispheres shut down at the same time.” Read more in this vintage article, Asleep in Flight.

Blackpoll warblers (Setophaga striata) are also champion fliers making a non-stop fall migration over the Atlantic Ocean of 1,900 miles in 72 to 88 hours. Traveling at 27 mph, they launch from the east coast between Nova Scotia and South Carolina and fly to their only stopover in Puerto Rico or Hispaniola (Haiti & Dominican Republic), then on to northern South America.

The blackpoll’s transoceanic path was proven in a 2015 study by Bill DeLuca and the Vermont Center for Ecostudies. VCE writes:

Bill DeLuca (Northeast Climate Science Center) and VCE solved this great modern-day avian mystery. Using light-level geolocators attached to Blackpoll Warblers in Vermont and Nova Scotia, DeLuca and colleagues documented the longest distance non-stop overwater flights ever recorded for a migratory songbird. During October, Blackpoll Warblers initiate a ~3-day non-stop transoceanic flight of ~2500 km from the north Atlantic Coast to Hispaniola and Puerto Rico. Radar data show migrating songbirds fly at 2,600 to 20,000 feet while making this journey. After a few weeks, they fly onto Columbia or Venezuela where they overwinter. Their spring migration route takes them over Cuba to Florida, where they journey up the eastern US seaboard to reach their breeding grounds in late May.

Vermont Center for Ecostudies: Blackpoll Warbler

Notice in this eBird abundance map for the week of 2 Nov that blackpolls are:

  • bunched up on the East Coast from Massachusetts to North Carolina
  • at a stopover on Puerto Rico and
  • early migrants have already arrived in South America.
Blackpoll warbler weekly abundance map, week of 2 Nov 2007-2021 (map from eBird Status and Trends)

Watch them throughout the year in this eBird abundance animation.

Blackpoll warbler weekly abundance map (animation from eBird Status and Trends)

Of course I wondered if blackpoll warblers sleep in flight during their 3 day transoceanic trip, but we won’t find out any time soon. Blackpolls are way too small to wear the sleep monitoring gear used on the great frigatebird.

(photo from Wikimedia Commons, maps from eBird Weekly Abundance; click on the captions to see the originals)

ebird species migration weekly abundance trends

The Essence of Iridescence

Anna’s hummingbird (photo from Wikimedia Commons)

16 July 2023

What causes iridescence? What makes a hummingbird glow red in one position, then dull green when he moves his head?

video from NDTV on YouTube

Other dazzlers, including beetles, shells, and rocks, have similar physical iridescent characteristics.

Six-spotted tiger beetle in Maryland (photo from Wikimedia Commons)
Nautilus shell sliced in half (photo from Wikimedia Commons)
Nautilus shell cut in half (photo from Wikimedia Commons)
Iridescence on anthracite, a.k.a. peacock coal (photo from Wikimedia Commons)
Sun dog — an iridescent cloud (photo from Wikimedia Commons)

Find out what causes iridescence in this 16 minute video from PBS @BeSmart. If you don’t have much time, watch the first 4+ minutes about hummingbirds.

video embedded from PBS @BeSmart

p.s. This article was inspired by All About Birds: What Is the Essence of Iridescence? Ask a Hummingbird.

(credits are in the captions, click the links to see the originals)

American Kestrels Mysteriously Decline

American kestrel at Madera Canyon, AZ (photo from Wikimedia Commons)

18 June 2023

When I began watching peregrine falcons 22 years ago, peregrines were endangered and our smallest falcon, the American kestrel, was doing just fine, but the tables have turned. Peregrines have fully recovered from extinction in eastern North America while kestrels have lost half their population and face an uncertain future. The New York Times described their plight this week in The Mystery of the Vanishing Kestrels: What’s Happening to This Flashy Falcon? Can we save this beautiful bird before it’s gone?

Pair of American kestrels in Colombia (photo from Wikimedia Commons)

American kestrels (Falco sparverius) range from Alaska to Tierra del Fuego and are the only “kestrel” in the Americas, but they aren’t true kestrels like those found in Europe and Africa. Instead, DNA tests have shown that our kestrel is closely related to the larger falcons of the Americas, including peregrines. Falco sparverius evolved to fill the kestrel niche.

Range map of American kestrel from Wikimedia Commons. purple=Year round, orange=Summer breeding, blue=Winter non-breeding

American kestrels are versatile birds. At home in grasslands, meadows, deserts, cities and suburbs, they eat grasshoppers, crickets, large flying insects, beetles, lizards, small rodents and small birds.

Kestrel eating a bug (photo from Wikimedia Commons)

Kestrels nest in cavities in buildings, trees, cliffs and nestboxes but more than half of their sites are unoccupied now in eastern North America. I’ve seen the decline first hand in Pittsburgh. A decade ago there were two kestrel nests within a few blocks of Downtown’s Third Avenue peregrines. Now there are none.

Dr. John Smallwood, a professor of biology at Montclair State University interviewed in the New York Times article, has monitored 100 kestrel nestboxes in New Jersey for nearly 30 years. The number of occupied nests at his sites peaked at 61 in 2002 and has dropped ever since.

What’s going wrong for kestrels? Are they out-competed for prey? Are they ingesting poison? What’s happening on their wintering grounds? Are insect declines affecting kestrels? Are neonicotinoid pesticides a factor? And what about the bigger questions of habitat and climate change?

Many kestrel experts think it’s a combination of causes. Dr. Smallwood agrees, but he still has a top suspect. “If I’m only allowed one word: grasshoppers.”

The one parameter that seems to be declining over time, researchers say, is survival of young birds in the summer.

… the thinking is that those juveniles may be more dependent on insect prey because it’s easier to catch.

— New York Times: The Mystery of the Vanishing Kestrels: What’s Happening to This Flashy Falcon?
Female American kestrel holding a cricket (photo from Wikimedia Commons)

I would not be surprised to learn that the kestrels’ decline is linked to the rapid insect decline in this century which was probably prompted by neonics. Neonicotinoids were first introduced in the 1990s but didn’t take off as a pesticide until the early 2000s.

Meanwhile a nationwide study funded by the USGS and the U.S. Fish and Wildlife Service is looking into the American kestrel’s mysterious decline. I hope they find the answer soon.

Read more at The Mystery of the Vanishing Kestrels: What’s Happening to This Flashy Falcon?

(photos and map from Wikimedia Commons, click on the captions to see the originals)

Canada Geese Can’t Fly in July

Canada goose molting primaries in late June, Ohio (photo from Wikimedia Commons)

14 June 2023

Once a year, from late June until August, Canada geese spend six weeks molting all their wing feathers. This means they can’t fly in July, nor even in late June.

On a walk at Herr’s Island yesterday I saw many Canada geese swimming in the river and a few of their primary feathers — the “fingertip” feathers — scattered on shore. At first I wondered if a goose had been attacked and then I realized the feathers were a sign of their synchronous molt. Here’s a snapshot from a similar discovery made by Rebecca Johnson in 2020. (Click on the snapshot to see her video on YouTube.)

Molted Canada goose wing feather (snapshot from Rebecca Johnson’s UA Museums video on YouTube)

Even if you don’t see discarded wing feathers you can tell a Canada goose is molting because its white rump is visible above the dark tail. It’s really noticeable from above.

Canada goose seen from above in the midst of wing molt in July (photo from Wikimedia Commons)
Canada goose in the midst of wing molt, late June, (photo from Wikimedia Commons)

Sometimes you can see the pin feathers coming in. This marked up photo highlights the pin feathers and visible white rump.

Closeup of Canada goose molting with markup (photo from Wikimedia Commons)

In late June and July when they cannot fly Canada geese are safe only in water. You’ll see them feeding just a short walk from a large body of water and notably absent from landlocked places.

When they can fly again, their tails will look like this when their wings are closed.

Canada goose in May in Chicago (photo from Wikimedia Commons)
Canada goose in March in Illinois (photo from Wikimedia Commons)

Have you noticed Canada geese avoiding people lately? They aren’t as bold when they can’t fly in late June and July.

(photos from Wikimedia Commons, wing feather snapshot from Rebecca Johnson’s UA Museums video on YouTube)

p.s. There’s a theory that this type of wing molt led to flightless birds in locations where threats were low. Read more about it at: Simultaneous wing molt as a catalyst for the evolution of flightlessness in birds.

Recognize Your Own Blue Jays

Blue jay (photo by Cris Hamilton)

10 May 2023

As humans we recognize each other by face, body shape and the way a person walks, but it’s rare that we can recognize individual birds. Birds move too fast to examine their faces and in most cases we don’t know what to look for. However if you can “hold them still” in photographs it’s possible to see patterns. This is especially true of your backyard birds that can be photographed over and over.

Blue jays all look the same … but not really. Their facial markings can be unique enough to tell them apart in photos. Lesley The Bird Nerd in Ontario, Canada has photographed her local blue jays for many years and learned to tell who’s who by face. Check out her 6.5 minute video below.

video embedded from Lesley The Bird Nerd

If you have a camera you can do this, too!

(photo by Cris Hamilton, video embedded from Lesley The Bird Nerd)