More Cooper's Hawk talk and a PS

Cooper's Hawk at sunset - 12/05
Photo by Cal Vornberger


A note just came in from Chris Lyons -- you may remember him from his comments about orange chest coloring on immature Red-Tailed Hawks. He is responding to John Blakeman's letter about Cooper's Hawks, which, in turn, was an answer to a query from Bill Trankle of Indianapolis. Got it? Good.

From Chris Lyons:

I enjoyed the exchange between Bill Trankle and John Blakeman, and I certainly concur that Cooper's Hawks are feisty unpredictable raptors, who will sometimes attack anything that moves. I once saw a young Cooper's Hawk join a group of crows chasing a Red-Tail over the marsh in Van Cortlandt Park, only to suddenly turn tail and fly back to cover, as if thinking "What am I DOING?"

However, I believe they do have a more sedate contemplative side. This past Sunday, we were walking through a little-trafficked corner of Van Cortlandt, when I spotted a medium-sized raptor on the path ahead of us. We were no more than 50 feet away, I'd estimate. The bird was a young Cooper's Hawk, and we realized it was standing in a puddle, while it stared off to the right of us, at nothing in particular that we could see. It was either unaware of or unconcerned by our presence (even though we'd been conversing rather loudly up to then, and continued to talk in more subdued tones while we watched it). No telling how long it had been there already, and we watched it for around five minutes before we moved a little too close, at which point it flew off to the right, and disappeared. A short time later, we saw it sitting in a tree, again staring off into the distance. My best guess is that the hawk came down for a drink, and stayed there a while because it simply liked the sensation of the cool water on its feet.

Unusual to see one hanging around on terra firma, but I've often seen one sitting in a tree perch for long periods of time. Energy conservation, not to mention hunting stealth (or digestion, after a hunt has succeeded), requires any raptor to spend a substantial part of its day more or less immobile--but Cooper's Hawks are certainly far less sedentary in their habits than Red-Tails. It may be humorous exaggeration to say they can't sit still for more than 20 seconds at a time, but sometimes hyperbole gets the point across nicely.

Did Bill Trankle's Cooper's Hawk have any chance at all of dispatching a fullgrown Fox Squirrel? It seems highly improbable, and it would unquestionably be dangerous for a Cooper's to try grabbing onto any mammal larger than a chipmunk (even the chipmunk's teeth could pose a threat). However, Cooper's Hawks have been known to prey on mammals much larger than a chipmunk, and there is an anecdote in Arthur Cleveland Bent's account of this species (From "Life Histories of North American Birds") that offers an intriguing explanation as to how they might be able to manage such a feat. M.P. Skinner, a very experienced naturalist, who contributed much valuable information to Bent's monumental work, witnessed this incident in Yellowstone National Park--

As I rode up the loop road through the aspens above Mammoth, I heard quick, frightened bird cries on either side, and I even seemed to sense the excitement in the air. I turned about to see what was happening and a Cooper hawk came shooting up the road past me, four feet above the road and going at great velocity. A Kennicott ground squirrel that no doubt had been attracted to the road by spilled oats, tried to cross the road only to be struck amid a cloud of dust. After striking the squirrel the hawk went on for six feet more before it could turn. Meanwhile the squirrel was stretched out in the road lifeless. The hawk came back and attempted to carry off its booty. But I dashed up at a gallop, and as the prey was too heavy to carry off quickly, the hawk had to drop it. I picked it up and found that only one claw had pierced the skin, and only a drop or two of blood had come out. So I believe that the squirrel was killed by the force of the blow itself.

http://birdsbybent.netfirms.com/ch1-10/coopers.html

It occurred to me that Skinner might have been mistaken as to the identity of the assailant--could it have been a Northern Goshawk? Unlikely such an accomplished hunter would have been an immature, and the adult forms of the two species are hard to confuse. A hawk much larger than a Cooper's would have no difficulty in carrying off a ground squirrel. In any event, the trust Bent places in Skinner's contributions makes it hard to believe he could have been so mistaken in his ID. The species most likely to be confused with the Cooper's Hawk is the Sharp-shinned Hawk, and that would be even harder to believe.

This is one isolated incident, of course, and the animal in question would not have been as large as a Fox Squirrel. Peregrine Falcons are known for using their ability to strike with great velocity from above, to stun or kill their prey--mainly birds in flight, not terrestrial mammals. Still, the principle is the same--immobilize the target by delivering a powerful blow from the air, thus avoiding a prolonged struggle which could lead to injury for the raptor in question. Easier said than done, I'm sure. But if the Fox Squirrel had been insufficiently alert, or had left itself in a vulnerable position for too long, it's conceivable that the Bill Trankle's Cooper's could have stunned it with a well-placed blow. One assumes this technique would require considerable practice, and perhaps only a small number of Cooper's Hawks ever become proficient at it--it's not likely that mammals ever make up the bulk of any Cooper's Hawk's diet.

It's much more likely, of course, that young hawk was not at all serious in its attack--merely indulging a strong instinct for aggression, or simply entertaining itself with a moving target. However, it could also have been 'testing' the squirrel--looking for signs of weakness, seeing if the animal would panic and leave itself vulnerable to the maneuver described by Mr. Skinner. For all we know, the hawk had never seen a Fox Squirrel before, and was trying to assess whether or not it was potential prey. The Cooper's Hawk didn't get its unfortunate reputation as a pirate of the barnyard (though probably preying on half-grown chicks most of the time) by being overly cautious and conservative in its hunting habits. With raptors in general, and accipiters in particular, the operative slogan often seems to be "L'audace, l'audace, toujours l'audace!"

PS from Marie:
Well, I'm a mammal bigger than a chipmunk, and I was once attacked by a Cooper's Hawk. True, I had wandered too close to a tree in which, unbeknownst to me, a pair of Cooper's were nesting. Nevertheless, if I hadn't dived to the ground as fast as I did, I might have made a nice snack for two Cooper's kids up there. [Just kidding. I know they would only have savagely raked my head with their talons.]