Naturespeak A naturalist's view of the world

December 23, 2009

The Wanderer Strikes

Filed under: Uncategorized — wykes @ 5:17 pm

The primary name of the Peregrine Falcon stems from the old-fashioned word meaning  “wanderer.” They are a global species, distributed over every type of habitat and on every continent except Antarctica, so this name is certainly an appropriate one.  Back in “the day,” however, they were better known as Duck Hawks. It used to be that most predatory birds were  named after their prey -even if the name was inaccurate or misleading. Cooper’s Hawks were notoriously called Chicken Hawks, Osprey were known as Fish Hawks, and Kestrals were dubbed Sparrow Hawks. Ospreys are indeed fish specialists, but Coops only take chickens when convenient and Kestrals aren’t happy unless they nab a regular diet of meadow voles. Although Peregrines take a wide variety of bird prey, they really do earn their Duck Hawk appellation.

Peregrines are not hawks in the specific sense of the word. They are falcons complete with long tails, tapered wings, and “sideburns” but let’s not get too picky here. “Hawk” is often used as a generic term to cover a whole host of daytime birds of prey. The sight of a Peregrine falcon atop a freshly killed duck is as natural as a winter sunrise itself. Since the Detroit River mouth environs offers a bounteous wealth of waterfowl this area acts as a magnet for these large falcons (duck a la Detroit). I frequently encounter evidence of their predatory work after the fact, but was lucky enough to come upon the scene of a fresh duck  kill along the river shore. As a matter of fact, this kill site was so fresh that the killer was still present at the scene (see below).

I was not witness to the killing act, but can piece together the probable scenario that led up to the scene before me. Peregrine Falcons are specialists at picking their prey out of the sky, so it is likely that this kill was made after the duck flushed from the water. Ducks that stay tight on the water surface or dive underneath it can avoid capture. Once in the air, however, the falcon is allowed to swoop down from above and strike the prey with a blow delivered by the feet -literally knocking the wind, if not the immediate life, out of his quarry. No one is really sure how fast a stooping falcon can go, but educated estimates exceeding 150 mph have been ventured. These birds become, in other words, living missiles.

As in war, however,  missiles do not always hit their target. Studies on the predatory habits of falcons have shown that they miss far more often than they hit their intended targets. In Alberta, Peregrines only nabbed 25 ducks after 275 attempts and in British Columbia they were batting nine out of 43 (I guess that would be a .200 average). It’s not just a Canadian thing either, it’s everywhere. If ducks knew the odds they’d be a happier lot of fowl.

The business of eating which follows the capture is conducted with little waste of time. Larger birds, such as eagles, often rob Peregrines of their kill, so they must get their job done efficiently. Plucking is the first order of business. All the contour and down feathers are pulled out – leaving the prey’s wings, head, and feet intact – before feasting begins. They can eat large amounts, up to 1/4 of their weight,  at one sitting. When I first came upon my falcon he had already performed the pluck and was well into the stuff portion of the routine. A large pile of down had accumulated on the downwind grass and his crop was bulging like a softball (you can see the round area in his throat in this view). Frankly he looked rather guilty about the whole thing and he moved a few feet away from the meal as I neared (see here). After a few minutes he returned to work (see here – sorry for the erratic camera work, there was an earthquake at the time).

This individual was an immature bird with quite a bit of brown streaking on the breast. The large sideburn marks along with the clear yellow eye rings were clear indications of the species, but I could not make a definite call as to the sex of the bird. Females (called “falcons” by falconers) are larger than the males (called “tiercels” by those same folks). If I had to guess, I’d say this was a female but I guess I don’t really have to guess do I?

Returning to the kill site later in the day, I was able to find out exactly what kind of duck served as the main course for this falcon. It was a Ruddy Duck – one of the hundreds of waterfowl currently wintering on the river. The victim was laid out in typical Peregrine fashion with the head, wings, and feet in untouched condition (see here). A portion of the entrails were neatly pulled out and laid upon the down patch. The nice condition of the duck’s head afforded an opportunity for a detailed look at that wonderful Ruddy beak (see below and here). Everything else on the bird was well picked over but a lot of meat remained in place.

When I returned to the kill the next day, the duck had been worked over yet again and most of the meat was gone. By the time I left the kill this time, the carcass was missing both its head and feet. I acted as the scavenger and removed those portions for further forensic study. You could say that the Peregrine and I were partners in crime.

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