Patience a virtue in identifying birds

Posted Aug. 14, 2009, at 11:14 p.m.

Birdwatching is an endlessly fascinating hobby. But as many bird watchers know, it can also be frustrating. Distance often makes characteristic field marks impossible to discern; it can also distort size. Additionally, the quality of light and time of day can distort color or render a bird into a monochrome silhouette.

Luckily there are other ways to identify elusive birds, as was dramatically illustrated for me one recent morning.

I was walking into work past a power-line clearing when I heard the alarm calls of songbirds within the shrubs. I wondered what had gotten them so riled up, and scanned the ground and sky for a predator.

My eye picked up the silhouette of a small bird perched on a power line overhead. It was far enough away, and the image indistinct enough that I could not discern what it was. Mourning doves often perch on those lines, and I thought the bird was about that size. But something about the shape seemed all wrong for it to be a dove. The tail wasn’t quite as pointed, but other than that I wasn’t able to tease out any other details.

I kept my eye on the bird. Hmm, I thought to myself. I wonder if that could be a kestrel.

Within seconds the bird launched itself from its perch. As it angled into the sunlight, I saw a flash of russet on its chest and in that moment I knew for sure: It was a kestrel.

The small falcon zipped over to an area of short grass and dove toward the ground, pulling up within a foot or so. At that distance I was unable to see if it had caught anything—it might have been after a dragonfly—and it returned to its perch to resume its lookout.

Were it not for the songbirds’ alarm calls, I might never have noticed the kestrel on the wire, nor given it a second look if I had. No mourning dove would have elicited such a response, and that’s what made me look more closely.

As the bird took to the air, it happened to catch the light just right to reveal the signature russet chest; no other North American raptor has this coloration. And although similar in size to the merlin — another small falcon — its method of flight was different; its wing strokes were shorter, more frequent, and more buoyant than a merlin’s powerful drives.

Kestrels most often prey upon small mammals such as mice and voles, insects such as dragonflies, grasshoppers, beetles, butterflies and moths; and small snakes and frogs. They will also take small songbirds, and from this arose their nickname “sparrowhawk.”

This falcon employs different hunting methods depending upon the prey being hunted and the habitat within which it hunts. If there are open perches available, the kestrel will “sit and wait” — actively scanning the area until an opportunity presents itself, then pouncing on its prey, be it a beetle or a vole. Interestingly enough, according to the “Birds of North America,” species account, studies done with the Eurasian kestrel—which is closely related to the American kestrel—”suggest that American Kestrels may be able to locate voles (Microtus spp.) by their urine trails, which reflect ultraviolet light visible to kestrels.”

In other words: the voles may run, but they can’t hide.

In the absence of perches, kestrels may hover-hunt—rapidly beating their wings to keep themselves more or less suspended in one spot—as they scan the ground for prey. They may not be as proficient at this maneuver as, say, a hummingbird—but their small size and buoyancy enables them to employ this method effectively enough.

Although kestrels are not specialized bird-hunters as are merlins and other falcons, they nevertheless can also pursue and capture winged prey in mid-air.

The variety and type of hunting methods this falcon uses are good identification clues; the overall buoyancy of its flight is another. If I had not seen the russet color of the bird in the power-line clearing, its light, fluttering flight would have clued me in immediately. There’s more than one way to ID a bird — sometimes it just takes patience to tease out the clues.

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