A few birds from the Yukon-Kuskokwim Delta.
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Red-Tailed Hawk:Red-Tailed Hawk Eskaviaq So, what do you think Red-tailed hawks and humans have in common? The nose, no, although we have heard of people referred to as “hawk-nosed.” Wings, definitely not, although many of us have tried to fly with artificial wings. Fingers, no, but our fingernails sometimes do look like talons. What about, yes, you guessed it, our eyes are located on the front of our heads, like the eyes of hawks. Look at a picture of a hawk head-on, and you’ll see what I mean. There is a reason for this. Early in our human evolutionary history this “binocular vision” came in very handy for us. Our distant ancestors, small tree-dwelling primates, had to be able to leap from limb to limb and snatch insect prey with their hands. Not an easy task unless you had sharp visual acuity, part of which derives from binocular vision. It was the same with the Red-tailed hawk and its broad-winged cousins. They needed these visual abilities to precisely estimate ever-changing distances to their constantly moving prey. Voila! Over the course of eons Mother Nature finally rotated their eyes toward the front of their head, so that the visual fields of the eyes overlapped; not as much as they do with us humans, but almost. I confess to never having seen this remarkable hawk out on the coast of the Y-K Delta, but inland I sometimes spotted one soaring low over the wooded hills. They were not common, possibly because of other hawk-eyed predators they had to compete with, such as Rough-legs, Gyrfalcons, Peregrines and Golden and Bald eagles. They are much more common in Interior Alaska, although the form usually found there has dark plumage, including its tail, and is often referred to as the Harlan’s hawk. I see them a lot during the summer, especially in the eastern Interior. The Red-tail is not only the commonest of all the broad-winged or buteo hawks, it is also the most variable, having at least 26 different forms. But they are all Red-tails, which means the behavior of Harlan’s hawks in Interior Alaska is the same as that of their red-tailed cousins on the Y-K Delta. In spring, after migrating back from as far away as Central America and Mexico, the male and female, who are thought to mate for life, find their original nesting territory, and immediately begin their aerial mating game, with the smaller male spiraling round and round the female, then suddenly stooping down like a falcon on her. She just as suddenly turns over in midair and presents her claws to his in mock combat. Then they’re off again soaring and circling about and screaming their shrill raspy cries at each other. During his spectacular maneuvering the male might even catch a prey animal and pass it to the female in midflight. They finally end this lovely aerial display by swooping to a perch in a tree and mating. Meanwhile, both birds have been building a nest in a tall tree higher than all the others. They usually construct it in the crotch of the tree in the form of a bulky bowl of sticks and twigs lined with finer materials such as green leaves, evergreen sprigs and strips of inner bark. The pair alternately may use one of several nests from previous years. 2-3 brown-spotted whitish eggs are laid and, although both parents incubate them, the female does most of this work while the male hunts for food and feeds her on the nest. The eggs hatch asynchronously (one per day or so) between 30-35 days later. The mother bird remains with the nestlings most of the time over the next few weeks while the male hunts for food (including small mammals, birds and large insects), which he brings to the nest, where the female tears it into small pieces to feed the young. After 4-5 weeks, food is simply dropped into the nest by both adults and the young feed themselves. The young finally fledge about 6-7 weeks after hatching and remain with their parents for several more weeks to learn some of their survival strategies. To be successful hunters themselves, the young Red-tails will be able to take advantage of the same hawk-eyed visual acuity their parents have. In addition to binocular vision, an important aspect of that acuity is the large size of their eyes; another is their telescopic vision, allowing them to see things many times closer than humans can. A Red-tail’s eye has a somewhat flattened lens placed rather far from the retina, giving it a long focal length, thus producing a larger image. Yet another reason these hawks are able to see better than we do is that their retina is packed tightly with “cone” receptors, which produce an exceptionally fine-grained image. Finally, Red-tails and other buteos have keen color vision, thus allowing them to distinguish their prey even better. With all of these advantages for survival, it’s no wonder Red-tailed hawks are the most common buteo in North America. Let’s finish with a few names for this amazing bird. Its Yupik name is Eskaviaq, which probably relates to the way the hawk scatters the remnants of its prey, especially smaller birds. The scientific moniker is Buteo jamaicensis, and takes its species name from Jamaica where the first specimens were collected (probably while they were wintering down there). In addition to the name we know it by, it has other common names: buzzard; buzzard hawk; eastern redtail; hen hawk; mouse hawk; red hawk; redtail; red-tailed buzzard; and western redtail. You usually hear this hawk before you see it. Listen for that shrill raspy cry you hear in the movies, and look up. Then grab your binocs and check it out.  |
