Friday, April 6, 2012

Accipiter Hawks

Sharp-shinned Hawk adult  perches in the snow on top of her prey 

At the Nature Preserve, I’ve been seeing more accipiter hawks as they migrate up from the south. Some of these hawks always stay with us during the winter; many of them adopt bird feeding stations as their hunting grounds. The more commonly encountered accipiter species are the Sharp-shinned Hawk and the Cooper’s Hawk. Both look nearly identical and they overlap in size. In fact the male Cooper’s Hawk is around the same size as the female Sharp-shinned (with hawks, the females are always larger than the males.)Though the generally larger Cooper’s Hawk sometimes takes small rodents, both hawks are primarily dedicated to hunting birds. In some circles, these hawks are considered to be backyard pariahs, since they prey on Mourning Doves and other popular songbirds. But these raptors are merely taking advantage of the concentration of bird life that is created by our artificial feeding stations. As our bird feeders draw songbirds out of the surrounding habitats, we give the accipiters obvious places to practice their trade. It has been shown that these hawks will develop a route consisting of many yards and birds feeding stations that they visit in a circuit.
Adult Cooper's Hawk - note his tail's  rounded edges 
More than a decade ago, I monitored some nests of Sharp-shinned Hawks. These stick structures were placed tightly against the trunks of Hemlock trees  –about 20 feet off the ground. The female did all of the work incubating the eggs and feeding the hatchlings. The male does provide the food (including a colorful array of songbirds), but will not directly bring the food to the nest. Instead, he drops it off at a prescribed location near the nest tree –this place is sometimes referred to as the "chopping block". It's thought that this arrangement stems from the relatively small male’s inherent fear of the female. He, after all, doesn't want to be mistaken for her next meal. The drop-off takes place with some haste, as the male anticipates his mate’s swift approach.
The Sharp-shinned has a straight or notched tail tip

A Juvenile Sharp-shinned Hawk
There may be 4 or 5 youngsters in the nest and when they leave or fledge, both parents will continue to provide them with food. Out of the nest, the young are pretty entertaining to watch as they play and chase each other through the woods –swooping between branches and otherwise practicing their much-vaunted accipiter maneuverability. The young unleash long siren like cries that are distinctly different than the staccato calls of the adults (the adult calls are commonly mimicked by Blue Jays).

Adult female Sharp-shinned Hawk
Breast feathers of an immature Sharp-shinned
Talons of a Sharp-shinned Hawk
It takes a couple of years for the Sharp-shinned and Cooper's Hawks to attain full adult plumage. 1st year birds has white mottling on their brown backs; they have a light colored stomach and chest which show prominent brown spots or barring. Their long tails are also brown and have several broad dark bands. The adults birds are quite beautiful; they have dark gray backs and gray tails that contain wide black bands. Their breasts feathers are light and show considerable orange barring. In all plumages these accipiter hawks have fluffy white feathers underneath  the base of their tails. Adult Cooper’s and Sharp-shinned Hawks have red eyes.

A visiting juvenile Northern Goshawk
The Northern Goshawk is the largest of our accipiter species and for us the one that is seen with the least frequency. I have experience with their nests as well –and it’s not the kind of experience that I’m likely to forget. Goshawks are very protective of their nest areas (they typically nest in larger forests with many conifers), and they won’t hesitate to chase off any intruder. I was rather vigorously repulsed when I got too close to one nest. The female especially came after me. While giving very loud “Kuk-kuk-kuk-kuk-kuk” calls, she swooped down on me and hit me on the back with her clenched talons. She did this multiple times until I had retreated far enough back to suit her. The male also joined in but did not make contact with my person. The next time I visited the nest area, I was really given the bum’s rush; I was escorted about a half mile down the road before they veered off and returned to their young.

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