Corvid Crossbill


Richard Bradus
 

Beautiful day, though quiet bird-wise.
Walking along California St. early this afternoon I noticed a few crows warily feeding on some food left out on a wall at the Shell station at the corner with Steiner St. It looked like one of the crows had made off with a piece of something, but when I got a closer look I realized that it had a weird looking beak, actually fully crossed upper and lower mandibles. I wonder if this was a recent deformity (from some trauma?) or a congenital anomaly (seems unlikely - could this bird grow to maturity with such a deformity?). Maybe it isn't really as limiting as it appears?





Never seen a cross-billed crow before!
Interestingly, later in the afternoon I was walking down to China Beach and a small flock of actual (Red) Crossbills flew over, calling as they went (maybe headed to Lobos Dunes?). Anyway, weird coincidence I guess.

Keep looking up!

Richard Bradus
San Francisco


Maureen Lahiff
 

It it likely to be avian keratin disorder, thought to be caused by a poecivirus.
(Virus named for chickadees.)

For a deep dive: https://pubmed.ncbi.nlm.nih.gov/33822149/

An article in the chain mentions American Crows,

Maureen Lahiff,
Oakland


-----Original Message-----
From: Richard Bradus via groups.io <grizzledjay@...>
To: SFBirds <sfbirds@groups.io>
Sent: Mon, Nov 14, 2022 5:04 pm
Subject: [SFBirds] Corvid Crossbill

Beautiful day, though quiet bird-wise.
Walking along California St. early this afternoon I noticed a few crows warily feeding on some food left out on a wall at the Shell station at the corner with Steiner St. It looked like one of the crows had made off with a piece of something, but when I got a closer look I realized that it had a weird looking beak, actually fully crossed upper and lower mandibles. I wonder if this was a recent deformity (from some trauma?) or a congenital anomaly (seems unlikely - could this bird grow to maturity with such a deformity?). Maybe it isn't really as limiting as it appears?





Never seen a cross-billed crow before!
Interestingly, later in the afternoon I was walking down to China Beach and a small flock of actual (Red) Crossbills flew over, calling as they went (maybe headed to Lobos Dunes?). Anyway, weird coincidence I guess.

Keep looking up!

Richard Bradus
San Francisco