|
|
|
Raptors Nonhuman residents of our rural landscapes |
|
A common sight in the Eastern Sierra is the soaring hawk making effortless circles over a field of grass and willows and cottonwoods. While the open expanses of our rural lands have clear value to residents, ranchers and to the many tourists who are drawn to the Eastern Sierra, the birds and animals that depend on these diverse and productive lands are a little less obvious. Perched on a cottonwood or fluttering above terrified prey, raptors find sustenance and shelter on the rural lands of the Eastern Sierra. The word "raptor" is applied to birds of prey. Among these raptor families are hawks, eagles, falcons, ospreys and owls. The ubiquitous Turkey Vultures in Inyo and Mono counties "have been found to be closer to storks, and have been reclassified in the past five years," says Tom Heindel. Tom and wife Jo, local ornithologists, are currently writing "Birds of Inyo County" and "Birds of Death Valley." Raptors have amazing abilities that enable them to thrive in our high desert area. Using their telescope-like vision, Red-tailed Hawks hunt while soaring high above ground. The Northern Harrier glides low over marshes and meadows using the element of surprise and sharp ears to catch mice, frogs and snakes. The Peregrine Falcon can reach speeds of 150 mph. when swooping down on a small bird. Many raptors migrate long distances. Some of the Swainson's Hawks that nest in the alfalfa fields of Hammil Valley may winter in Argentina while the Ospreys that nest at Mono Lake may be spending the winter in Chile. Though most birds die in the first year of life before leaving the nest, the life span of an adult raptor can be well over twenty years, depending on its size. "There was an albino Red-tailed Hawk living north of the Bishop golf course for twenty two years," Tom Heindel recalls, "though such longevity is atypical." A raptor's life span is usually proportional to its size, so a larger bird, like a Bald Eagle, could live upward of twenty years while a hawk would normally only reach fifteen. There are laws in North America that protect raptors from human predation, but the more imminent threat these birds face may be the destruction of their habitat. Many of the aerialist raptors, like the Red-tailed Hawks abundant in the Owens Valley, usually have contiguous populations, where one population of hawks flows into the next. This provides an ecological benefit by increasing variance in the gene pool, but also requires a contiguous ecosystem. Although, a few raptor species may prey on chickens or trout, raptors are for the most part very beneficial to people and to agriculture in particular. Many farmers and ranchers recognize the benefits of having raptors such as the Swainson's and Red-tailed Hawks nesting on their lands. These birds provide excellent gopher and ground squirrel control as the adults capture and feed these rodents to their young. The Heindels affirm that, "many raptors do great good as they keep rodent, rabbit, and grasshopper populations from reaching the huge numbers that would seriously damage crops." Owls, who "take over the bird of prey niche during the night," are appreciated increasingly throughout California as rodent exterminators. Because a single family of Barn Owls can eat over 1,000 gophers a year in addition to other small mammals, such as mice and moles, many farmers are preserving nest trees and building owl nest boxes in order to encourage the birds to stick around and control rodent populations in their fields. Because they feed at the top of the food chain, raptors also act as indicators of the condition of their ecosystems. The health of the raptor populations is important because it depends on and therefore demonstrates the health of the entire ecosystem underneath. Some raptors are specialists (like the Peregrine Falcon, who only preys on other birds) and some are generalists, but as predators they rely on healthy prey populations that themselves rely on adequate animal and vegetable food sources. In return, raptors keep prey populations in check and help maintain the balance of the ecosystem.
|
|
