All About The Cooper's Hawk At Union Bay

Here is a recent post from the Union Bay Watch Blog published by Larry Hubbell, long-time local photographer and birder.

Here also is an in-depth article about Larry and his work.

Persistence

While heading home, after a visit to the Union Bay Natural Area on Saturday, I thought my 'birding' for the day was done. I was wrong. It was just before 3 p.m. when a startled dogwalker pointed out this avian interaction and visually suggested restraint.

I assume, the Cooper's Hawk had just captured the Rock Pigeon, otherwise, there would have been a lot more feathers surrounding the scene.

The hawk mantled the prey, e.g. it used its wings and tail to hide the pigeon, while it continued to pluck feathers. Mantling reduces the chances of a larger predator seeing and stealing the meal. The list of creatures who could easily disturb a small hawk is long. At a minimum, it includes our local Bald Eagles, a passing Red-tailed Hawk, Gulls and of course American Crows. 

In addition, a Raccoon, a Coyote, a River Otter or even an off-leash Dog could easily scare a small, male Cooper's Hawk off of its prey. All of these potential interlopers have been seen around Union Bay. The hawk's cautionary instinct is not a frivolous behavior, however, the plucking seemed a bit presumptuous.

The plump pigeon was still actively objecting to the idea of being a belated Thanksgiving dinner for an inexperienced young hawk. Since a Rock Pigeon and a male Cooper's Hawk can be similar in weight the result of their interaction was not a foregone conclusion.

For the young hawk, a meal of this size might make the difference between surviving the winter, or not. The struggle continued. With each passing moment, the young hawk's predatory skills seemed to increase, while the odds for the pigeon decreased.

With a smaller bird, like a Dark-eyed Junco, the hawk's talons would be relatively longer. This would enable the hawk to quickly pierce a vital organ and dispatch the prey far more quickly and humanely. 

On the flip side, the similar size of the two birds still gave the pigeon a chance.

When another inadvertent pedestrian approached too close, the Cooper's Hawk momentarily released its prey. A larger or more experienced hawk might have attempted to carry its meal to an elevated perch. The large, horizontal, moss-covered branches of a Big-leaf Maple tree are prime feeding sites for experienced Cooper's Hawks. The upper branches of maple trees provide cover from airborne interlopers, while the elevation of the mid-level branches slows down the approach of most mammals.

Given a split second of respite, the pigeon flew. The pigeon's instincts were good. It dived into a nearby thicket of cattails, bushes and small trees. The hawk gave chase but the highly motivated pigeon dived deeply and hid well.

After about five minutes, the hungry young hawk popped out of the thicket with just one, small, downy feather stuck to its bill. 

The persistent little hawk seemed to consider its options while listening for any sound of the pigeon attempting to escape its fate. Given the hawk's persistence, I am thinking we should call him, 'Percy'.

After a few moments of rest, Percy turned and clearly considered resuming the hunt. From this angle, we can see that his crop, the area just below the throat, is still relatively small. The crop enables predatory birds to consume their prey, fairly quickly, before retiring to a safer location to digest their meal. Somewhat, similar to sitting on the couch and watching a football game after consuming your Thanksgiving Dinner. 

If you read last week's post, you know the vertical stripes on the chest of the hawk tell us this is a first-year bird, but how do we know it is a male. In this case, the answer is related to the 'jewelry' on the hawk's left leg.

This particular hawk was 'banded' by a team from the Urban Raptor Conservancy (URC) on July 17th, 2018, in Laurelhurst. Given that female raptors are generally larger than males, the team deduced this bird was a male Cooper's Hawk and banded it with a purple band on the left leg. With females, they use an orange band on the right leg.

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In addition to studying Cooper's Hawks and Peregrine Falcons, Ed Deal explains that the Urban Raptor Conservancy is embarking on a new project, 

'Right now our primary focus is on fundraising for our cooperative study with PAWS - testing dead raptors for rat poison residues. Our goal is to determine the baseline level of exposure in hawks and owls in Western WA......which has never been done.  We have enough money to send off a test batch of 5 samples to make sure all systems work.  We hope to get that done in the next week or two.  PAWS has 35 more samples in the deep freeze....at $100 a sample we have a lot of grant writing and fundraising ahead of us...'

Today, Cooper's Hawks, Barred Owls, Bald Eagles (and sometimes even pets) consume live rats who may carry rodenticides within their bloodstreams. The bioaccumulation of rodenticides can easily kill predatory creatures. A critical step to reducing this inadvertent destruction is to prove the frequency and existence of the poison. You can help by donating via the Urban Raptor Conservancy website, please Click Here.

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Percy dove back into the thicket.

Initially, he was visible among the many small red branches.

As he moved lower into the cattails he became harder to follow. Soon, he disappeared completely. An occasional abnormal wiggling of the cattails was the only clue that the hunt continued. I watched and waited.

Finally, more than twenty minutes, after the Rock Pigeon's escape, Percy appeared with the pigeon in tow.

As the young hawk began to eat I realized this was another unique opportunity. I wondered, How long would it take for a Cooper's Hawk to consume a full meal? Ten minutes passed.

By the way, I promise not to expose you to any of the more explicit photos.

Twenty minutes passed. Between each bite, the young hawk would raise up and check for potential intruders. Thirty minutes passed and the pace of his eating did not change.

After 50 minutes, the hawk's crop was quite visibly extended.

 I was beginning to wonder if Percy would ever get full.

Finally, after an hour of feeding, he took a few last looks at the remains of the meal before flying off to the northeast. Percy quickly disappeared in the direction of the Union Bay Natural Area.

It turns out that a full meal for a Cooper's Hawk is similar in length to a human lunch hour. Of course, about half of that time was spent watching for potential bullies and thieves. Surprisingly, while sitting on the ground and fully exposed, Percy ate the full meal without interruption. This was not the safest choice, but it worked. Percy still has a lot to learn but with continued luck and his natural persistence he has a chance to survive the coming winter. Please keep your eyes open and watch for Percy. The numbers on his purple band are '2' over '4'.