Category Archives: Bird Behavior

1,500 Chimney Swifts

Chimney swift trio (photo by Jeff Davis)
Chimney swift trio (photo by Jeff Davis)

11 September 2020

In September chimney swifts (Chaetura pelagica) migrate through western Pennsylvania on their way to South America. Unlike songbirds, swifts migrate during the day but we often don’t see them because they travel so high. Birds of the World says they’ve been recorded above the clouds on the warm leading edge of a cold front, 7000 feet up!

At night swifts sleep in chimneys, choosing the most convenient place. The roost may hold more than 1000 birds per night though the individuals change as some leave for the south and others arrive from the north.

Since moving to Oakland in early August I now live within sight of the Cathedral Mansions chimney, one of the largest migratory roosts in the Pittsburgh area. When the weather’s fine I step out to watch them circle the chimney and dive into the roost. Last Sunday I invited Michelle Kienholz to join me. Her videos show some of what we witnessed.

Chimney swifts swirling around Cathedral Mansions chimney, 4 Sept 2020 (photo by Michelle Kienholz)

We started watching while the sun was up but the swifts didn’t come close to the chimney until a few minutes after sunset. By that time it was obvious they were making very large circles around the chimney, flying out of our peripheral vision.

As the sky got darker the swifts circled closer and closer, faster and faster. To enter the chimney they stalled upright, then dove in. There were so many swifts they had to wait in line or circle out and try again.

We tried to count as they dove in but they were quick.

It was almost too dark to see when the last swift disappeared 20 minutes later.

My estimate was 1,500 chimney swifts.

Watch them live at the Audubon Society of Western Pennsylvania’s Virtual Chimney Swift Night Out, 25 September 2020, 7-9pm. Click here for details.

p.s. The swifts leave before dawn if the weather is good but this morning it’s overcast. A few swifts popped out of the chimney 15 minutes before dawn but all went back in.

UPDATE 18 SEPT 2020: I counted 1,300 chimney swifts tonight. The flock completed its dive into the chimney by 7:52pm.

(photo of three swifts by Jeff Davis; still shot and videos of Cathedral Mansions chimney swifts by Michelle Kienholz)

Geese At Work

Geese at work, protecting the flock (photo from Wikimedia Commons)

On Labor Day let’s honor working birds. This year … domestic geese.

A couple of domestic geese are often kept with chickens to guard them from predators. Geese are always alert and will naturally honk and shout when they see danger. The chickens run for cover while the large and aggressive geese may attack the threat. Some geese are so aggressive that they’ve injured people. (By the way, Canada geese will attack if you approach their young.)

A farmer who used geese and guineafowl to guard his chickens says domestic geese are the best. Geese alarm only when they see a threat; the farmer knows there’s a good reason to check on the flock. Guineafowl are noisy but they alarm for almost anything.

When you see geese with chickens you can be sure those geese are at work.

p.s. When seen in Pennsylvania, geese like those pictured above are barnyard escapees. Here are some tips on their background: Chinese geese have long necks and knobs on their heads (top photo) and were domesticated from swan geese (Anser cygnoides). Domestic geese in white or gray with faces like snow geese (the attacking goose above) are descended from greylag geese (Anser anser).

p.p.s. Sometimes the geese are fooled. In Medieval manuscripts, stained glass windows and carvings a fox dressed up as a monk or priest preaches to geese and chickens, then ultimately eats one of them. “When the fox preaches, look to your geese.

Fox preaching to chickens and a goose from Book of Hours, Maastricht, 1st quarter of 14th century (image from Wikimedia Commons

Convergent Behavior

Eurasian wryneck (photo by Imran Shah via Wikimedia Commons, Creative Commons license)

Did you know that, when threatened, this Eurasian woodpecker uses the same distraction display as a South American flycatcher? Though the birds aren’t related their similar behavior looks like convergent evolution.

Convergent evolution is when similar traits evolve in unrelated species because they’ve had to adapt to similar environments.

A classic example is the body shape of sharks and porpoises. Both have long streamlined bodies, dorsal fins and flippers because both must swim fast to catch underwater prey.

Black-tipped reef shark, Maldives (photo from Wikimedia Commons)

But sharks are fish and porpoises are mammals. They aren’t related.

Long-beaked common dolphin (photo from Wikimedia Commons)

Here’s another example of convergent appearance.

Eastern meadowlark, yellow-throated longclaw (photos from Wikimedia Commons)

The eastern meadowlark of North America (a member of the blackbird family Icterid) and the yellow-throated longclaw of Africa (a member of the wagtail/pipit family Motacillidae) live in similar habitats on separate continents. Though strikingly similar they are not related.

So what do you think? Is the neck-turning behavior of the Eurasian wryneck (Jynx torquilla) …

… like the distraction display of the royal flycatcher (Onychorhynchus coronatus) of Central and South America?

Royal Flycatcher (Onychorhynchus coronatus) display

(Video courtesy of Cameron Rutt via Flickr; see more about this bird here).

While they’re unable to escape both birds twist their necks. Perhaps the goal is to mesmerize the predator. It looks like convergent behavior to me.

p.s. See more examples of convergent evolution at this Univ of Texas link.

(photos from Wikimedia Commons. Videos by Anders Nielsen on YouTube and courtesy of Cameron Rutt on Flickr)

Leaves Early To Raise Another Family

Male orchard oriole (photo from Wikimedia Commons)

Why haven’t I seen an orchard oriole (Icterus spurius) in Pittsburgh since June? They probably left early on migration. Some have a reason to hurry — they raise a second family in Mexico.

A 2009 study by Rohwer and Hobson found that some yellow-billed cuckoos, orchard orioles, hooded orioles, yellow-breasted chats and Cassin’s vireos breed in North America, then on their migration south they stop off at the thorn forests of western Mexico and raise a second family.

This “migratory double breeding” discovery was stunning. Scientists knew of just two Old World species who did this on their journey north, but until this study no birds were known to do it in the western hemisphere and none anywhere were known to double-breed on the southbound trip.

Gathering the evidence was daunting. July and August are monsoon season in western Mexico with temperatures at 100+ degrees, humidity at 100% and lots of biting insects.  Rohwer’s team was there to study the molt cycles of migratory songbirds.  Instead they found five species breeding! In addition to orchard orioles they found …

… the tellow billed cuckoo (Coccyzus americanus) that breeds in eastern North America and western Mexico:

Yellow billed cuckoo (photo by Chuck Tague)

Hooded oriole (Icterus cucullatus): breeds in southeastern Texas, the Southwest, parts of California and western Mexico.

Hooded oriole (photo from Wikimedia Commons)

Yellow-breasted chat (Icteria virens): breeds across the U.S. and into southern Canada and Mexico.

Yellow-breasted chat (photo by Anthony Bruno)

and Cassin’s vireo (Vireo cassinii): breeds in the Pacific Northwest, southwestern Canada and surprisingly in western Mexico.

Cassin’s vireo, New Mexico (photo from Wikimedia Commons)

Who would have guessed they’re in such a hurry to raise another family half a continent away.

(photos by Chuck Tague, Anthony Bruno and from Wikimedia Commons)

Surprising Enemies of Paper Wasps

Black-capped chickadee (photo from Wikimedia Commons)

21 August 2020:

The presence of European paper wasps (Polistes dominula) can be daunting until you realize they have enemies. Birds eat their larvae right out of the nest. Gerardine Baugh discovered this while watching a chickadee at a wasp’s nest outside her window.

Who knew that a chickadee would be so brave when confronted by a wasp?

p.s. If you missed it, learn more about European paper wasps in this week’s article.

And there’s good news from Ohio: When European paper wasps first arrived in Ohio they supplanted native paper wasps. Now that trend has reversed.

(photo from Wikimedia Commons; video by Geradine Baugh)

Show Me Your Hands

Striped cuckoo (photo from Wikimedia Commons)

Riffing on cuckoos …

Like the common cuckoo and brown-headed cowbird, the striped cuckoo (Tapera naevia) of Central and South America is an obligate brood parasite. Called “saci” in Brazil or “sinfín” for its voice, this bird is more often heard than seen and that’s a shame because his behavior is so fascinating. When approaching an unknown saci, here’s what he does:

Whoa! Where did he get those hands?

All birds have them. They’re actually the bird’s thumbs. The complete structure with three to five short feathers is called the alula and is used to prevent a stall during slow flight. Pitt peregrine Dorothy demonstrates them while soaring in this 2008 photo.

Alulas visible as Dorothy soars (photo by Jack Rowley)

The saci has black alulas that contrast with his white breast feathers so they stand out when he dances.

Mighty impressive. Show me your hands!

p.s. The striped cuckoo is called the saci in Brazil because it is related the saci of Brazilian folklore. Read more here.

(photos from Wikimedia Commons and by Jack Rowley)

Cuckoo Mimicry, Back and Forth

Adult common cuckoo (photo from Wikimedia Commons)

As a brood parasite, the common cuckoo (Cuculus canorus) gets away with laying its eggs in other birds’ nests because it’s larger and uses mimicry to fool its hosts.

Our own brood parasite, the brown-headed cowbird, uses stealth to dump her eggs but a female cuckoo doesn’t have to be sneaky. She looks like a sparrowhawk, the Eurasian version of our sharp-shinned hawk, so naive songbirds scatter when she shows up.

Also, her eggs closely mimic those of her favorite hosts: dunnocks, meadow pipits, and reed warblers. Here are four clutches of reed warbler eggs with a single cuckoo egg laid in each. The cuckoo egg is quite similar though larger. (Check yesterday’s blog for photos of a reed warbler and meadow pipit feeding cuckoo chicks.)

Four clutches of reed warbler eggs parasitized by a single (larger) common cuckoo egg (photo from Wikimedia Commons)

While the cuckoo mimics features of other birds we mimic him. Here’s a real cuckoo calling…

… and our mimicry of the cuckoo in a Black Forest cuckoo clock.

Cuckoo mimicry back and forth.

(photos from Wikimedia Commons; click on the captions to see the original)

If You Think Cowbirds Are Bad …

Just like brown-headed cowbirds (Molothrus ater), common cuckoos (Cuculus canorus) in Eurasia are obligate brood parasites that never raise their young. Cuckoos lay their eggs in the nests of smaller birds that foster the cuckoo chicks as their own. A stark difference between cowbirds and cuckoos, though, is their size. Cuckoo chicks can be 10 times larger than their hosts!

Compare the Eurasian reed warbler (Acrocephalus scirpaceus) feeding a common cuckoo chick, above, to the brown headed cowbird chick with its song sparrow (Melospiza melodia) foster parent below.

Brown-headed cowbird chick begging from song sparrow host (photo from Wikimedia Commons)

The cowbird is slightly larger than its host but the cuckoo chick when it leaves the nest will be 10 times the reed warbler’s weight.

This situation can be even more bleak, as shown in a Twitter post by John Deakins.

So if you think cowbirds are bad, consider common cuckoos.

p.s. I asked folks to tell me the identity of the foster parent standing on the chick’s back. Janet Campagna suggests meadow pipit — which looks right to me. Meadow pipits are one of three species most often parasitized by common cuckoos.

(photos from Wikimedia Commons plus an embedded photo from Twitter; click on the captions/tweet to see the originals)

What’s That Whining Sound?

Juvenile red-tailed hawk, Washington DC, 2017 (photo from Wikimedia Commons)

Have you heard whining that sounds like this?

Sometimes you hear songbirds calling nearby, “Danger! Watch out!”

In July and early August young red-tailed hawks whine for food. Here’s one in July 2018 at New York’s Botanical Garden with an American robin raising the alarm.

And here’s one on a windowsill in Austin, Texas, July 2011.

Red-tailed hawks raise one brood per year. The female lays eggs in March or April. The eggs hatch in 28-35 days and the young fledge 42-46 days later. That’s when the begging begins.

For three weeks juvenile red-tailed hawks depend on their parents and are not shy about asking for food. Whine!

The whining doesn’t end there. Though the youngsters become increasingly self sufficient they still want a handout if they can get one. Whine! Whine! Whine! Their parents ignore them.

Self sufficiency is the first big hurdle on their way to becoming successful adult red-tails. Some youngsters take longer than others to get the hint.

Meanwhile, whine, whine, whine, WHINE!

(photo from Wikimedia Commons; click on the caption to see the original. Audio from Xeno Canto, videos from YouTube)

Mixed Up Ducks

Mixed up ducks in Germany (photo from Wikimedia Commons)

One of the challenges of city birding is identifying the mixed up ducks not found in any field guide. These “mutt ducks” are the hybrids of mallards paired with escaped domestic ducks.

It’s easy for domestic ducks to hybridize with mallards because nearly all of them(*) are descended from mallards (Anas platyrhynchos).

Mallard cross with a domestic duck (photo from Wikimedia Commons)

Mallards hybridize with wild ducks, too, as shown in this a mallard X gadwall mix.

Mallard X gadwall hybrid Brewer’s duck (photo from Wikimedia Commons)

Some ornithologists worry that mallards will hybridize their closest relatives — American black ducks, Mexican ducks and mottled ducks — out of existence, as in this mallard X Mexican duck mix.

Mallard X Mexican duck hybrid (photo from Wikimedia Commons)

But perhaps they’re forgetting how recently those species evolved from mallards. The Mexican duck (Anas diazi) that occurs in Mexico and the U.S. Southwest was thought to be a subspecies of mallard until 1957.

Mallards are just working on creating new species. 😉

Read more about mixed up ducks in this vintage article: Ugly Ducks

(*) Some domestic ducks are descended from Muscovy ducks.

(photos from Wikimedia Commons; click the captions to see the originals)