You've probably seen those little "hawks" that perch on power lines. Well, they're actually falcons, and, from my experience, they'll eat anything. You have to agree; the other day—at 15-degrees below zero—I watched a healthy-looking adult female perched on the power line just east of Sisters, in the process of gulping down what appeared to be a sagebrush vole.
That same day, I also saw a baby kestrel in the process of swallowing a full-grown western fence lizard, and then found another nestling kestrel with a baby quail foot sticking out of its mouth. The final truth of the matter is, a kestrel is not far removed from its ancient ancestors, theropod dinosaurs of the Mesozoic Era; they too swallowed everything whole.
Much of the hunting is done by the mother kestrel, who has laid and hatched sometimes up to 5 eggs in a nesting box. Hunting lizards, for example, is a common practice; after all, the lizard is loaded with rich, protein-saturated eggs, a perfect source of energy to help the kestrel's babies grow into healthy adult kestrels.
She will swoop down and seize the lizard in her needle-sharp talons—like the raptor she is—and drop all her weight on it so it can not squirm away. Using the incredible power of the tendons operating the talons, she literally will squeeze the life out of the lizard. (Raptor in Latin is, "to seize.") Raptors also have tiny tactile "hairs" (feathers, really) around the nostril that sense movement in prey.
Once the victim is dead, the falcon heads for home with it—which, in itself, is a feat. The lizard weighs about a third of the falcon, so she's into a critical flying mode—having almost exceeded her gross carrying capacity—huffing-and-puffing to get home with her protein package for the kids. When she sees the opening of her home—in this case a beautifully constructed plywood nesting box—she sets a course for the center of the entrance hole and sails right through it.
It is at that split second she uses the attribute that all falcons possess, a long, stiff tail. As she passes through the entrance hole—doing about 30 mph—she drops her tail and slams it against the front of the box. The stiff tail, which is normally used for steering, becomes a very efficient brake; it stops her from crashing into the back wall of the box and she literally drops in on her kids, lizard and all.
The first nestling to open its mouth gets the lizard, head first and then sits there breathing through that wonderfully designed trachea in its tongue, slowly digesting said lizard for about three days—or—if the lizard is taking up too much breathing space, it will do everything it can to upchuck it, where it will then become a target for siblings, or torn apart by one of the adults.
Which takes us back to the Mesozoic Era; fossils of early bird-like dinosaurs have been found with full-grown prey within the skeleton. Today, you can dissect an owl, hawk or eagle, and you'll find whole prey inside the viscera. Nature certainly understands, "If it ain't broke, don't fix it."
Over the last 12-or-so years—with the aid of Don MaCartney of Bend, and a wonderful bunch of volunteers—I have been looking into American kestrels, the smallest of the falcons in this hemisphere. They use nesting boxes to raise young in, and I've been banding the babies with a tiny, aluminum numbered band issued by the USGS Banding Lab. Don got me started and he and his volunteers keep it going.
We had one of the kestrels from a nesting box in the Sisters Country turn up in Sacramento for winter (another bander caught it while trapping and banding raptors and released it). And last year the Bird Banding Lab notified me of a band from a kestrel banded at a nesting box from Bend, recovered near Tijuana, Mexico—right across the border from SanDiego; which makes sense. Humans aren't the only ones who become "snowbirds" in winter.
Also, in the time we have monitored kestrels, we have found dragonflies, adult ant lions, beetles, grasshoppers, lizards, snakes, mice, voles, gophers, kangaroo rats, and an assortment of small birds in the gullets and food remains.
It takes a lot of fortitude to analyze the contents of the nesting box after the kestrels have all taken wing and the box deserted. The stuff left behind can only be described as awful offal. As with all raptors (and some waterfowl and songbirds) kestrels upchuck pellets containing indigestible components packed into a tight bundle, small enough to pass up and out the throat.
The liquid feces, mutes, which is usually white and black, is made up of digestible parts of prey, and squirted with great vigor (the term is "slicing") all over the inside of the nesting cavity, walls, ceiling and everything else in the box—sometimes each other—and dries like cement.
(Early falconers, when choosing their hunting falcon, such as a Peregrine or Gyrfalcon, would observe the bird squirting the fecal material and note how far it went. They judged the strength of the bird on how far it could slice.)
They are remarkable "hawks."