30 August 2023
In August in the East End of Pittsburgh we get a taste of November dusk. It isn’t the weather or the clouds or the time of sunset. It’s a flock of more than 100 crows, a hint of the thousands to come this fall, that gather on rooftops along Neville Street before flying west to roost.
This year in early August the crows were absolutely silent but as the month progressed a few spoke out, telling me they were in a mixed flock of American and fish crows. American crows (Corvus brachyrhyncos) say “Caw.” Fish crows say a nasal “Uh-oh” (Corvus ossifragus). It’s the only reliable way to tell them apart.
American crow: “Caw Caw Caw.”
Fish Crow: Nasal “Uh oh”
I wanted to count by species but the crows remained silent and unidentifiable through most of the month. I tried to tell them apart by sight but my focus on appearance made it impossible to count. So I stop trying. My August eBird checklists place all of them as “American crows” with an X for “Fish crows present.”
Then suddenly last Saturday they were all “talking” and about three quarters of them were fish crows. The flock continued on Sunday evening but I was too busy to count. I shouldn’t have assumed they’d be here on Monday. They were gone and they haven’t been back.
The big flocks will arrive in late October, comprised of 90+% American crows.
For now we’re in the Calm Before The Crows.
p.s. eBird’s Fish Crow Weekly Abundance map shows a dot in Pittsburgh in the month of August … and then it’s gone. Watch the animation here.
(credits are in the captions)
Fish crows, hmm. How sure are we that these are a separate species than the American crow?
When the were mostly on the coast and fairly separate, I could see this maybe, but now they are comingling with American crows here in landlocked Pittsburgh.
Maybe I am just stuck on the old AP biology definition of “species” I learned: two organisms are different species if they cannot mate and produce offspring that can also reproduce. I’d suspect fish crows and American crows can and do produce viable offspring. Correct? I mean I am totally guessing there, but I just can’t see how they could be such different species when they are just a little different in size and call.
Well, they really are separate species and have not (as far as I know) been nominated for lumping. They have different nesting habits which make them less likely to pair up: https://www.birds.cornell.edu/crows/hatchrep.html
Even two species that already hybridize, or instance Carolina & black-capped chickadees, are still separate species.