26 October 2022

During the summer corvids stay home to raise their families but as soon as the breeding season is over they move around. In autumn large flocks of American crows return to Pittsburgh to join the winter roost while a few common ravens show up, alone or in pairs.

This month the crows and ravens are back in town. Since August their populations have gone through several phases.

Late August: On 30 August a surprising count of 380 fish crows gathered on rooftops at Fifth & Craig while only 12 American crows were present that evening.

September: By 6 September fish crow numbers dropped to 30 and then zero. American crow numbers rose through the hundreds. No ravens.

October so far: On 10 October a high count 620 American crows flew past “the doorknob” water tower at dusk. By late October no crows were counted because they changed their route. However we now see and hear ravens!

Ravens in town?

Crows migrate. Adult ravens stay home year round. However, young ravens go wandering until they reach sexual maturity at three years old. From fall through early spring a handful of these ravens visit Pittsburgh.

Last Sunday 23 October Andrea Lavin Kossis saw two ravens on Dawson Street dining on some “delicious roadkill.” The pair even had something to say about it.

Brock! Brock!

p.s. In December I’ll enlist your help to find the crow roost in time for the Pittsburgh Christmas Bird Count.

(photos by Andrea Lavin Kossis and Kate St. John)

6 March 2022

Sometimes an experiment doesn’t work as planned but the results are far better than expected.

Researchers wanted to track Australian magpies (Gymnorhina tibicen), a very social species that lives in groups of 2-12 individuals on permanent territories. Rather than use the typical long-lasting harness that requires recapturing the bird to collect the datapack, they designed a harness that would release when exposed to a magnet placed at a feeding station. Would the new harness design work? The first step was to try it on a few magpies and see.

Researchers led by Joel Crampton captured five magpies at Pacific Paradise, Queensland, banded them and fitted each one with a GPS harness. Then they followed the birds to see the harness release at the feeding station.

Each banded bird immediately tried to remove the harness but it was too well designed for that to work. Instead the unexpected occurred. Unbanded magpies came to the rescue.

On the day of trapping, one individual was observed attempting to remove its own tracker but was then approached and aided by another juvenile (without a tracker or coloured leg-band) once again pecking the harness part of the tracker. The tracker remained but, within the next 10 minutes, an adult female (also without a tracker or leg-band) proceeded to approach and successfully pecked the harness at various points such that the tracker came off the fitted juvenile within c. 10 minutes. This first Magpie that had been tagged had its GPS device removed within 1 h.

— Australian Field Ornithology: Australian Magpies Gymnorhina tibicen cooperate to remove tracking devices

This happened over and over again until none of the banded birds had trackers. Here’s a video of the magpies helping each other.

This finding was unexpected but far better than the original experiment. It was the first time anyone had seen rescue behaviour among Australian magpies.

To our knowledge, this is the first study to report the conspecific removal of GPS trackers, and should be considered when planning future tracking studies especially on highly social species.

— Australian Field Ornithology: Australian Magpies Gymnorhina tibicen cooperate to remove tracking devices

“Here,” say the magpies to each other. “Let me help you out of that.”

p.s. A tip of the hat to Michelle Kienholz for pointing out this study.

(photo from Wikimedia Commons, diagram and video from Australian Field Ornithology: Australian Magpies Gymnorhina tibicen cooperate to remove tracking devices; click on the captions to see the originals)

24 February 2022

Corvids [crows, jays, magpies] occupy virtually every terrestrial habitat on Earth, including Arctic tundra, arid deserts, urban streets, and tropical rainforest. Having likely dispersed around the world over millions of years from an Australasian core, it is odd that they never reached New Zealand or Patagonia or disappeared from them both.

— Birds of the World: Corvidae account

It’s hard to imagine a place without any crows or jays but it is true of the southern end of South America, New Zealand and quite a few Caribbean and Pacific islands. I learned this seven years ago when I visited a place that has none of them: St. John, U.S. Virgin Islands.

In the absence of intelligent omnivorous corvids, other birds fill their niche. The all-purpose crow/jay/predator at St. John is the pearly-eyed thrasher (Margarops fuscatus) …

… an aggressive, opportunistic omnivore that feeds primarily on large insects, but also feeds on fruits and berries, and will occasionally eat lizards, frogs, small crabs and other bird’s eggs and nestlings.

— Wikipedia: Pearly-eyed Thrasher account

He acts like a jay, hunts like a corvid, and eats like a crow. I think he looks more aggressive than a blue jay. Maybe it’s the pearly eye.

On Throw Back Thursday, learn about this thrasher in the corvid niche in this 2015 article:

13 December 2021

If something doesn’t look right, crows are quick to point it out and warn each other.

Ten years ago Pittsburgh’s winter flock saw something very disturbing and circled above it in the half light before dawn. “Watch out! Watch out! It’s dead! Watch out!”

Three hours later a person discovered the disturbing scene. It prompted an investigation.

The crows saw it first. Here’s the story.

(photo from Wikimedia Commons; click on the caption to see the original)

28 November 2021

Smart crows are naturally wary around humans. Though most people don’t even notice birds, crows know that some humans are malicious.

Crows notice us noticing them. They watch us back while they assess whether we’re dangerous or beneficial. They learn the faces of enemies so they can recognize them later. They also remember their friends.

A friendship with crows can run both ways when the crows bring gifts.

An “enemy” can become a friend if he’s consistently kind and trustworthy, as was this mailman in Vancouver, BC.

Peanuts were the treat that turned an “enemy” into a friend.

(photos from Wikimedia Commons and Felip1 via Flickr Creative commons license. Embedded videos from YouTube. Click on the captions to see the originals)