Saturday, September 30, 2006

How does Pale Male stay on that flagpole?

A reader, Karen Anne Kolling, wondered how Pale Male manages to keep a grip on that smooth, round ball atop the Belvedere Castle flagpole. Lincoln Karim, who took the picture, wondered as well on his website .Here's John Blakeman's explanation:


I, too, saw Lincoln's pondering of this question.

Actually, Pale Male is not physically gripping the sphere at all. He's merely perched on top of it. From the tossed feathers on the side of his head you can see that there is a slight breeze up there, but it's not enough to push him over. He's standing very erect, which also indicates that the winds are light. If they were stronger, he'd be leaning aerodynamically into the wind.

Therefore, the hawk is perched here in just the way my rural red-tails sit on the tops of wooden utility poles, which are flat or only slightly sloped.
Red-tails, and most other birds, too, can balance effortlessly on narrow perches. PM is balanced on this perch. He's not physically gripping it with any force. When I'm hunting with my red-tail Savanna, she, too, sits erect on my gloved fist, which is even smaller than this brass sphere. As we walk through a meadow searching for prey, she balances instantly as my fist moves back and forth. She does not tightly grip my fist at all. She merely sits and balances on it. It's actually quite remarkable, her ability to minutely shift leg and body muscles to accommodate our mutual motions (which are not unlike the motions encountered by the hawk on a small tree branch on a windy day).
Red-tails sitting in trees on small, waving branches, use the same techniques. It's primarily continually re-adjusting balance, not a firm, locking grip.

But the birds will use a locking grip when sleeping. They have a rasp-engaging set of circular muscles and tendons that wrap around the vertical tendons that extend between the leg muscles and the toes. When the bird goes to sleep on a windy night, she takes her perch and then tightens and locks the encircling muscles and tendons around the leg tendons. She falls asleep with the legs locked in a firm grip on the branch or other perch.
But I've seen red-tails just at dawn's first light sitting on a large, flat surface, where they couldn't have gripped anything. They slept the night through merely standing on the flat ledge. Any wind gust would have knocked them over during the night. But it appears that red-tails are rather able to discern the night's weather before they retire. If it's going to be a windy night, the bird will almost always select a branch perch around which they can lock their legs for the night. Just how they know if a night will be windy or not is not clear, but they seem to be very accurate in these predictions.

Lastly, however, we know that if weather changes, the birds can and do fly around at night to new or better perches. Having watched my trained red-tails for several decades, I believe that they can see at night just about as well as we can, so they can stubble upon a new branch if they have to.

That shot by Lincoln was pretty fine -- regal, if you will.

John Blakeman