AUTUMN 2008/VOLUME 22, NUMBER 4
Up Close with Crows
Kevin McGowan, Cornell Lab of Ornithology associate and co-editor of the second New York State Breeding Bird Atlas, is an authority on the crow family, and has done extensive research in social development, family structure, and West Nile virus transmission, especially on American Crows. Anyone who spends time in Ithaca, New York, will eventually spot one of “Kevin’s crows,” sporting colored leg bands and tags on its shoulders. Kevin has been keeping track of the crows in the Ithaca area since 1988. Some of his marked birds have been reported from as far away as Pennsylvania, West Virginia, and Boston.
What was your most thrilling encounter with a bird?
Probably one of the most thrilling things that ever happened to me was when I was checking a crow nest and as I was measuring one of the eggs, it hatched—right in my hand! And that little pink thing came out, about as big as my thumb. That was pretty cool.
What is one thing you wish everyone knew about crows?
I wish people understood that the groups of crows they see are often families, not gangs. People attribute some sort of malicious intent to what crows do when they’re just trying to raise their kids like everybody else. It would be nice if people actually thought about it as mom and dad and the kids from last year who are still helping them raise young. It’s not a bunch of juvenile delinquents coming through and trying to cause trouble.
At what point do nestlings become wary of people?
There is a behavioral shift less than a week before they come out of the nest. They leave the nest at approximately 35 days. They’re tame and friendly and assume you’re going to give them food up until about day 25 or 26, and by day 28 they’re ready to jump away from you. It’s a logical progression. Up until that point, there’s nothing they could do if you were going to eat them anyway, to get away and survive. But once they get big enough to be able to jump out of the nest and run away, there’s a survival value in doing that. If a parent mobs, usually what the kids do before day 25–28 is hunker down. But after that age, when the parents call they get up and get ready to go.
When people pick up baby crows after day 20 or so they don’t tame down that well. Most of the ones that are heavily imprinted and follow people around were taken home earlier.
Without shoulder tags would all crows look alike?
A few birds are distinctive enough, either from an injury or a white feather or something like that, that we can distinguish them. With backyard birds, you can say, “I know that’s the male because he stands tall and has a thick bill and that’s the two-year-old son because he has a thinner bill.” But if you saw them away from home—and they wander all the time—there’s no way in the world you could identify them. It’s hard enough when they have bands and tags.
How are crow numbers changing?
They’ve been slowly increasing since the 1960s across most of the Midwest and the East. Whether they were more abundant before agriculture declined a bit, we don’t know. In the ’80s, crows started moving into towns and urban areas to breed. That may have added to the population, although it didn’t change the numbers as much as it changed people’s perceptions. Suddenly there were crows in backyards, and so people thought the population must be expanding. “And they’re bigger than they used to be!” No, they’re closer to us than they used to be. That’s the only difference.
When West Nile virus hit, it changed the trajectory of the populations in most places. Here in central New York, it stopped the increase, and there was a slight decline. We lost about 50 percent of our population over about two years, but they bounced back. They’re cooperative breeders so they were in families of about six individuals anyway, so half the population could be killed off and still have the same number of nests in an area. There was a cushion effect so they didn’t get hit as hard as if they were breeding in single pairs.
Indiana and Illinois lost more than 75 percent of their crows. Ohio Breeding Bird Surveys went from the highest in 40 years to the lowest in 40 years in just one year, and they haven’t recovered there. So in some places it was a fairly strong positive trend going up and up and up and all of a sudden it’s down and they’re not recovering.
More information about Kevin and his research, and FAQs about crows, can be found at www.birds.cornell.edu/crows.
For permission to reprint all or part of this article, please contact Laura Erickson, editor, Cornell Lab of Ornithology, 159 Sapsucker Woods Rd., Ithaca, NY, 14850. Phone: (607) 254-1114. email: email@example.com