Monday, October 5, 2009

A Tale of Two Kestrels

Female American Kestrel. Photo by Keith Bauer.

Male American Kestrel. Photo by Doug Brown.

They’ve been called ‘sparrowhawk’ for their habit of preying on songbirds, but in actuality, insects, small lizards and mice are more common fare for North America’s smallest falcon, the American Kestrel. About the size of a robin, the kestrel is four ounces of power-packed muscle, sinew, and determination, trademarks of the little guy, the one who flies harder and fights tougher.

I once watched a male kestrel take on a female Cooper’s Hawk that had intruded into his territory. The Cooper’s Hawk is a bird-eating specialist and no slouch in the flight department, regularly capturing and killing birds as large as pigeons and even pheasants. It also weighs about four times as much as a male kestrel. The little guy’s only advantage was the speed and agility common to all falcons. I heard his battle cry, “killy, killy, killy” long before I saw anything. Within a few seconds, a harried looking coop flapped furiously away from the white cliffs where the kestrel pair were nesting with the little guy in hot pursuit. He would rise above the coop, and then plummet down to attack her back, over and over. In one instance, she turned just as he reached her, rolling onto her back and presenting those dangerous feet right in his face. In that same instant, I knew that he was a goner and that his mate would not be able to rear their clutch of young alone. But, pluck and perseverance served him well, and I watched them fly off together into the distance with the smaller figure keeping up a relentless attack, dive-bombing her repeatedly as they flew out of sight. A few minutes later, he returned victorious, circled the cliff, and took up his position above the nest cavity near the top of the cliff where he could continue his daily patrol, keeping all intruders away from his family.

Kestrels build their nests in cavities, ranging from tree cavities to holes in cliff faces to cracks in the eaves of buildings. A couple of years ago, a pair successfully reared four young in the cavity of an expansion joint of interstate 40 where it crossed the Rio Grande in Albuquerque. The cavity ensures that the female and young are well protected from the elements and other predators. It also makes monitoring nest success a challenge because the young are not visible until after they emerge. Within the first few days after the young falcons leave the nest, they are flightless. There isn’t enough space in the cavity for them to stretch their wings and exercise their flight muscles. However, their lungs and voices are fully developed and it is a simple matter to spot the youngsters loudly begging, killying, and calling from their various perches. If you keep a watch on a falcon family, you’ll notice that the babes have very short tails, perhaps an adaptation for the cramped quarters of their nursery. Within a few days, however, the young falcons master flight and the entire family leaves the area.

Like all falcons, kestrels have black eyes, and are built for speed with long, pointed wings. However, the similarity with their larger cousins, the merlin, peregrine falcon, and prairie falcon, ends there. The kestrel is a predator but, as a small bird, it is also prey. They have two spots on the back of their head, called false eye spots. The purpose of these spots is to confuse a predator that might attack from the rear into thinking that it is tackling the kestrel head on, and give the falcon a better chance to escape. Kestrels also have two black vertical stripes on their heads, one directly below the eye, and the other slightly farther back. The purpose of the dark mark, called a malar stripe, is to reduce glare from the sun, much like that of football players that paint a black stripe below their eyes.

Males and females have different plumages, and can be easily identified. Females have a back and tail with horizontal brown and black bars with a vertically streaked breast. The more colorful males, have handsome bluish gray wings, a clear buffy breast, and a striking rufous tail with a single black bar at the end.

In fact, I once heard a story from one of our volunteers, a young birder named Lindsey Porter. Because Lindsey and her family are such strong supporters of Hawks Aloft, we asked her to do the honor of giving our newest educational bird, a male American Kestrel, his name. She thought about it for several days before deciding. She told me that when she was learning about raptors, a man told her that she could always tell the boy kestrels from the girl kestrels because every day when the boys got up, they put on their blue Superman cape! We call Lindsey’s kestrel, Clark Kent.

Kestrels adapt well to human activities and often live near businesses and homes in both urban and rural areas. Many people welcome the plucky little birds with the big attitude, not just because they are entertaining, but because they help to reduce rodents and insects. You, too, might be able to attract a kestrel family to your property, particularly if you live near open fields with an abundance of food. Kestrels are known to adapt well to artificial nest boxes. You can find several different nest box plans on the World Wide Web as well as pre-made boxes ready to install in your backyard.