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.) [Illustration: 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.] [Illustration: 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.] [Illustration: 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.