TEXT! While often considered barren and relatively devoid of life, the Desert Life Zone supports a surprising diversity of plants and animals, some of which are found nowhere else on earth. In fact, desert ecosystems have long proven a magnet for birders and naturalists wherever they occur on the planet. In North America, the primary desert types are the Mojave, Sonoran, and Chihuahuan, as well as the desert occupying the Great Basin.Perhaps the lowest common denominator in all desert environments is aridity, or dryness. Water is often at a premium in the desert, either because it seldom precipitates or because when it does, the precipitation is not readily obtainable by desert organisms, due either to rapid run off, rapid evaporation, or the season at which the precipitation occurs. A consequence of these factors is that many desert organisms have evolved often creative ways of obtaining and conserving moisture, even amidst their arid surroundings.Desert vegetation is unique in its appearance, often featuring plants with tiny leaves or thorns instead of the broad, moisture-squandering leaves more typical of forest plants. Cacti are prominent and diverse in certain desert ecosystems, and probably reach their zenith in the Sonoran deserts of the American Southwest. In certain of the high deserts of the western United States, plants like sagebrush and a mixture of various grasses and shrubs intermingle to form habitats that in some ways are more reminiscent of grassland environments than of the classic image of a desert filled with cacti and rattlesnakes.Bird life often abounds near water holes and riparian streams in the desert. In fact, in certain areas of California and the Southwest, such desert oases have proven to be better places to find migrant concentrations and out-of-range vagrants than in many other areas of the surrounding countryside.Some characteristic birds of the Sonoran desert ecosystem are Harris' hawk, White-winged Dove, Greater Roadrunner, Elf Owl, Gila Woodpecker, Brown-crested Flycatcher, Verdin, Cactus Wren, Curve-billed Thrasher, Phainopepla, Pyrrhuloxia, black-throated Sparrow, and Scott's Oriole. Needless to say, the composition of such a list for each desert ecosystem would be different, since different indicator species would take the place of the ones listed above.
