That so many varieties of birds can co-exist in the same area is possible because different species generally do not compete with one another for the same food source. Each gleans its food in a slightly different manner and locale. Each species vigorously defends its territory from others of its kind but will tolerate neighbors that occupy a different niche in the community. A single plum thicket may contain the nests of a pair of catbirds, mourning doves, robins, and vireos. Because each bird hunts its food in a slightly different manner and place, they do not directly compete.
The cliff-nesting swifts and swallows have reappeared above the river, a twittering confusion of swirling, darting shapes that manage to survive by capturing insects on the wing. Higher up, the booming of nighthawks announces that insects are active in the upper air also.
After supper I walk along the river. Now that shadows fill the river bed, there might be an opportunity to see a beaver working or a mink hunting along the shore. Passing close to where the meadowlarks have their nest, I cause a panic of concern. Both birds, invisible a second ago, lift off the ground, scolding and threatening, to distract my attention from the location of the nest. The outcry brings a killdeer up from the shore of the river. Uttering its plaintive, reedy cry, it circles about, lands, runs rapidly along the bank, then crouches down to display a “broken” wing. It is joined by a mate and both birds take up the act, leading me away from their own eggs or helpless young hiding motionless on the ground. So adept are the killdeer at this diversion, it seems incredible that instinct and not intelligence is responsible for their highly specialized behavior.
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A Sanctuary for Birds
Among those birds living in the forest at the base of the Tower is the white-breasted nuthatch, which commonly makes its fur- and bark-lined nest in the cavity of a tree. Many a woodland hiker has paused for several minutes to watch this inquisitive, sparrow-sized bird creep head first down the trunk of a tree, stopping now and then to look out at a 90 degree angle. The red-breasted nuthatch also inhabits the park.
The intense sky-blue of the male mountain bluebird catches the eye of the most casual of birdwatchers. Its blue breast distinguishes it from the western bluebird. Like the white-breasted nuthatch, this bird nests in a tree cavity, usually a deserted woodpecker hole. It often hovers low over the ground, then darts down to catch insects.
Though small in area, Devils Tower National Monument provides a sanctuary for an extensive variety of birds. Because the mountains and the plains converge here, species common to both can be found. More than 90 species have been counted.
Several large birds may be seen flying around or near the Tower itself, occasionally swooping down to prey upon life in the open grasslands. These include Cooper’s and red-tailed hawks; American kestrel; golden and bald eagles; prairie falcon, and turkey vulture. Only the prairie falcon and the rock dove, or pigeon, live on the Tower. (See pages [60]-61 for photographs of the golden eagle, prairie falcon, and burrowing owl.)
Standing still or in flight, the black-billed magpie is distinguished by its white shoulders and belly, by white patches under its wings, and by its long tail.
The nighthawk nests in the open grasslands here. This robin-sized bird was mistaken for a hawk by the pioneers because of its long wings and swift flight.
The red-headed woodpecker spends most of its time in the open deciduous woods. Its entirely red head and a large white patch on its wings distinguish it from other species.
The meadow across the river is a solid yellow of blooming spurge. In contrast, the ground on the Monument side of the river presents only a few isolated plants, and they are limp and pale from the effects of herbicide. Because spurge is an exotic plant that invades grasslands and displaces native flora, it is exterminated, through selective application of herbicide, within the Monument boundaries.
The rattle of a kingfisher precedes its sudden appearance around the sharp bend in the river. Skimming low across the water, the blue and white bird darts upward to perch on a cottonwood snag that overhangs the river. Its large crest and straight bill make the kingfisher look more caricature than real. Intently studying the river below, it need not wait long before plummeting from its observation post straight into the water. Reappearing a second later, it quickly regains its perch, the silver glint of a small fish caught in the parted scissors of its black bill. After swallowing the fish with a toss of its head, it shakes the water from its feathers and resumes its patient inspection.
Like a giant, soundless mosquito, a cranefly rises upward from the river bank. Another hovers low across the surface of the water, frequently dipping its abdomen below the surface to deposit its eggs. The first quickly disappears with the banking flight of a nighthawk; the second with the darting intercept of a dragonfly. Like countless other species of insects that divide their lives between the water and land, the craneflies are a living link in the food chain that helps bind the aquatic and terrestrial life communities together.
The many thousands of insect species requiring an underwater environment for their larval stage help sustain many species of terrestrial predators when the insects emerge from the water as adults. The kingfisher that nests here and the occasional great blue heron that stops during migration also enjoy the fruits of the water community, taking fish and frogs. But the process is not a one-way street. Nutrients leached from the land help fertilize the aquatic food chain. And the grasshopper that inadvertently hops into the river, only to disappear quickly into the gullet of a fish, represents another of the ongoing exchanges between land and water.