Landscape-level Population Dynamics of an Avian Habitat Specialist Invading an Alien Grassland in Southeastern Arizona

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9815293BockThe Botteri's sparrow has almost disappeared from the American Southwest due to drought and overgrazing. This bird, a tallgrass specialist, is usually now restricted to stands of scaton grass in lowland areas. In this native grassland that can grow over 2 meters tall, the birds conceal their nests from predators at the bases of these tall grasses and then forage on adjacent slopes for grasshoppers and other insects. Recently, these birds have begun nesting in native upland grassland areas where the grasses are shorter than the tall stands of scaton grass, but grasshopper densities are high. In addition, they also nest in areas where the cover is dominated by introduced African lovegrass, where the cover is nearly as heavy as the native scaton. However, in these areas, grasshoppers are relatively scarce. This unique situation allows for testing of hypotheses and predictions of landscape ecology, sink/source and metapopulation dynamics and the ecological impacts of alien vegetation. This research will answer such questions as: What is the relative importance of grass cover (safe nesting habitat) versus food availability (high grasshopper numbers) to reproductive success in the Botteri sparrow? What are the combined contributions of the three habitats (sacaton, native upland grasslands and exotic grassland) to regional population dynamics of the Botteri sparrow and how these relate to the sink/source status of the entire species population at the northern margin of its range? In addition, it will address whether the exotic grasslands represent a suitable habitat for the birds or are the introduced grasslands an ecological trap for this species.