Avian assemblages on altered grasslands

作者：Fritz L. Knopf · 发表于：Digital Commons - University of South Florida (University of South Florida) · 年份：1994 · 被引用次数：416 · 研究领域：Rangeland Management and Livestock Ecology、Wildlife Ecology and Conservation、Ecology and biodiversity studies

Grasslands comprise 17% of the North American landscape but provide primary habitat for only 5% of native bird species.On the Great Plains, grasslands include an eastern component of tall grasses and a western component of short grasses, both of which have been regionally altered by removing native grazers, plowing sod, draining wetlands, and encouraging woody vegetation.As a group, populations of endemic bird species of the grasslands have declined more than others (including neotropical migrants) in the last quarter century.Individually, populations of the Upland Sandpiper and McCown' s Longspur have increased; the wetlands-associated Marbled Godwit and Wilson' s Phalarope appear stable; breeding ranges are shifting for the Ferruginous Hawk, Mississippi Kite, Short-eared Owl, Upland Sandpiper, Horned Lark, Vesper, Savannah, and Henslow' s sparrows, and Western Meadowlark; breeding habitats are disappearing locally for Franklin' s Gull, Dickcissel, Henslow' s and Grasshopper sparrows, Lark Bunting, and Eastern Meadowlark; and populations are declining throughout the breeding ranges for Mountain Plover, and Cassin' s and Clay-colored sparrows.Declines of these latter three species, and also the Franklin' s Gull, presumably are due to ecological phenomena on their respective wintering areas.Unlike forest species that winter in the neotropics, most birds that breed in the North American grasslands also winter on the continent and problems driving declines in grassland species a...