By Jeannie Marcure
Although my years of bird watching have familiarized me with many of the beautiful birds in our area, I have to confess that when it comes to raptors I’m still often frustrated by my inability to make positive identifications.
Most people tend to think of all the day-flying birds of prey with hooked beaks and claws as one group while actually they fall into two quite separate families. The hawk group is comprised of kites, eagles, buteos, accipiters and harriers, while the falcon group is comprised of falcons and caracaras.
Sibley describes falcons as compact, fast flying raptors with long pointed wings, long tails and notched beaks. Although members of this family vary greatly in size, all are well adapted to swift level flights, twisting flight maneuvers and high speed dives while in pursuit of prey. Because of their proficiency in flight, they can be hard to spot and to identify. The good news is that the smallest member of this family, the American Kestrel, is very common in the Flathead Valley and can often be seen on fence posts and utility wires throughout the area. At about the same size as an American Robin, the Kestrel weighs approximately 4 ounces–the weight of a stick of butter. Despite its small size the Kestrel can fly at 40 miles per hour and can hover over potential prey like a small helicopter. In fact it is the only small hovering hawk found in North America. The Kestrel is also the only small raptor that has a bright rust-colored back and tail. It also has white cheeks, a gray crown and two black mustache marks on its face and is easily differentiated from Sharp-shinned Hawk which is of a similar size but much less colorful and lacks the mustache markings. The other similar species, the Merlin, is much darker and has only a single mustache mark.
As is the case with many of the raptors, the American Kestrel females are larger than the males with females measuring 9 to 11 inches in length and weighing an average of 4.2 ounces, while the males measure 8 to 10 inches and weigh an average of 3.9 ounces. Experts speculate that this reverse sexual dimorphism occurs because raptors eggs are quite large in relation to the size of their bodies and the female’s larger size gives her an advantage in both the egg laying and in the brooding.
According to Wikipedia, Kestrels form strong pair bonds and courtship begins shortly after the male establishes a territory. In our area most Kestrels are migratory but our annual Christmas Bird Count data shows that some usually over winter. In the 32 years of the Bigfork count, Kestrels have been present in 12 of those years with the highest occurrence being 7, while in the 7 years of the Kalispell count, Kestrels have been reported in 6 of the 7 years and the numbers have ranged from 1 to 4.
Kestrels are secondary cavity nesters preferring to use old woodpecker holes or natural cavities in trees or in rocks. They will also use nest boxes constructed to the proper size. I found great directions for building nest boxes for Kestrels (and many other species) here. Returning migrants commonly re-establish their territories from the previous year and in early courtship the male may make “dive displays”, a series of climbs and dives of 33 to 66 feet with 3 to 5 “klee” notes given at the peak of each ascent. He may also present the female with food during a ritual courtship feeding and try to entice her to the nest by calling and “flutter-gliding” toward her while carrying food. In response she may beg for food while doing a similar “flutter-glide”. No nest is built in the cavity but if you’re providing a nest box you could add some sawdust or wood shavings for the eggs to rest on.
Once the nest is established and the 3 to 7 eggs are laid, both sexes take turns incubating the eggs, a very rare occurrence among birds of prey since the female usually incubates exclusively. Both the male and female Kestrel develop bare oval patches on the sides of their breasts where the bare skin can warm the eggs. Eggs typically hatch after about 30 days and the young grow quickly becoming noisy between day 11 and 14 and reaching adult weight in about 2.5 weeks. First flights are taken between days 26 and 31. Cornell Lab reports that Kestrels take care of the house keeping tasks in their nest by backing up to the wall and squirting their feces onto the walls. The feces then dry and stay off the eggs and later the baby birds. You can imagine what a smelly place that nest must be by the time the nestlings fledge!
In the summer, Kestrels feed primarily on insects such as grasshoppers, dragonflies, and crickets, and on small mammals such as mice, and voles. In the winter, however, the absence of an insect supply in our area forces Kestrels to feed primarily on small mammals and birds, or to migrate far enough south to obtain an adequate food supply. Interestingly, the Mission Valley, reputed for its large population of voles most winters, usually records a much higher number of Kestrels on its Christmas Bird Count.
Kestrels are plentiful in our area and seem to be adapting well to the changing landscape of our valley so take time this month to get out and enjoy our beautiful valley. When you do, remember to watch the roadsides for a small, rust colored bird and maybe you’ll be lucky enough to observe one of my favorite birding sights– a Kestrel perched on a fence post or a utility wire, proudly holding a mouse in its foot! Don’t forget to take your camera, that will be a scene you’ll want to record!