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. _continues on page 46_ A Sanctuary for Birds [Illustration: 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.] [Illustration: 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.