Tuesday, June 14, 2005

[But what about us humans?] Blakeman reassures about the hawks and the heatwave

Many hawkwatchers and readers of this and Lincoln's website have been worrying about New York City's heatwave and how it might affect the Trump Parc hawk family. John Blakeman sends a reassuring letter:


Marie,

With temps in the mid 90s,the Central Park red-tails are going to get as uncomfortable today as the humans there. But this isn't the first time red-tailed hawks have had to endure such extremes. If this weather were truly destructive, red-tails would have died out a long time ago. How many days in the last hundred years or so have reached 95 degrees?

Our hawks will pant, with their beaks open, and appear to be downright uncomfortable. They don't like this weather any more than we do. Red-tails much prefer the coldest weather in winter over summer heat. In winter, they just eat some more food and turn up the physiological body furnace. But in summer, the hawks still have all their winter clothes (feathers) on, and they can heat up pretty quickly. We falconers know that a hawk kept in a heated car or building can quickly die. Don't misunderstand. Normal summer heat is difficult for the birds. But it won't kill them. The species has been through this hundreds of thousands of times before.

With their dark, sun-absorbing thick feathers, the adults heat up quickly. They will compress their layers of feathers tight against the body, to facilitate outward body heat transfer. Red-tails in the summer heat will appear markedly thinner than in the winter, when they fluff up their feathers to create microscopic airpockets that insulate and reduce body heat loss.

If an adult's internal body temperature elevates to over 105 degrees F for a period of time, the bird is in trouble. But it won't just sit there and die of hyperthermia. On hot days such as these, the bird can set its wings and in just a few minutes be soaring at several thousand, even 10,000 feet. Up there, it can be only 50 or 60 degrees F, and the bird can reduce its internal body temperature down to a very cool (relatively speaking) 95 degrees.

Of course, it won't take but a few hours or less to warm back up again, so the bird will be fighting the heat all day. It also will perch in among tree leaves, out of the direct heating blaze of the sun. I've never encountered a free-flying adult red-tail that has been killed by any summer heat. Remember, this species lives very nicely in the Sonoran Desert of the southwest where temperatures commonly elevate into the low hundreds.

<>And for those wondering why the birds don't just drop in for a cooling bath in any of the several Central Park lakes or ponds, such water resources simply don't exist in large regions occupied by the red-tail in the West. Taking a bath has its own problems. Doubtless, the wet feathers provide delightful cooling, but this doesn't last long as the water quickly evaporates. Secondly, the water in the feathers adds significant weight, that for flight must be compensated by strenuous flying -- which creates more internal heat. Taking a bath isn't a real solution to the problems of late afternoon heat for our red-tails. Mostly, it's just a matter of endurance, just as it was for other New Yorkers before air conditioning. (As readers may have noticed, I tend to compare the immigrant Central Park red-tails with the many human immigrants that, for three centuries, have made New York such a great city. Please excuse my extrapolation of human experiences upon those of the hawks, as romantic as that might be. But at least in the case of summer heat, the parallel fits.)Worry not. The adults will survive.

What about the two eyasses? Well, Pale Male, Jr. and Charlotte have been very good parents. They have been mantling, spreading their wings over the little ones, keeping them, for the most part, out of the direct sun. But worry even less for the eyasses than the adults. So far, the little birds haven't been much able to maintain a very consistent body temperature. We know that when hatched, and for the first 7 to 10 days, the eyasses are "cold-blooded," meaning that they can't really regulate body temperatures around a desired, normal central point. That's why the parents are very diligent in sitting over them when first hatched. The little eyasses get warm only by crawling up under a sitting parent.

But just about now, in the late second week or so, the birds start to keep warm by themselves, generating sufficient heat. Therefore, the hot sun is not much of a problem at all. They can rather easily handle the elevated afternoon temperatures. They just won't be generating so much physiological heat from their food. Instead, biochemical energy will be used to synthesize new feathers, not to stay warm.

The heat is to move on out on Wednesday or Thursday, and things will become more "normal." In all likelihood, all four of the Trump Parc hawks will come through famously.
Everyone else, keep cool, keep calm. There's nothing out there red-tails haven't dealt with before.

Sincerely,

John A. Blakeman