Stopover Habitat Selection by Migrant Landbirds in a Fragmented Forest-Agricultural Landscape

[摘要] Limited stopover habitat along migration routes is a possible contributor to population declines in migratory landbirds. In highly fragmented agricultural landscapes, potential stopover sites are often limited to riparian corridor forests and small forest patches, but there are little quantitative data on stopover habitat selection in these areas, especially with regard to how migrants use isolated versus connected, and riparian versus upland, habitat patches. We examined the use of upland forest woodlots in the forest—agricultural landscape of northwest Indiana as stopover habitat, to determine whether migrants selected stopover sites on the basis of proximity to riparian corridor forest. In two spring and two fall seasons, we conducted 384 surveys in 12 small woodlots at three levels of isolation from a riparian forest corridor, detecting 3,695 en-route migrants of 76 species. We detected no difference in migrant abundance or species richness among distance classes in either season, and a principal-component variable comprising several woodlot isolation metrics was not a significant contributor to migrant abundance in linear regression models. Fall migrant abundance was positively associated with early-successional forests containing fruiting trees and shrubs, whereas spring abundance was not associated with any vegetation characteristics. The lack of patterns of habitat occupancy at the landscape level suggests that migrants select stopover sites on the basis of local habitat characteristics such as food resources, regardless of the landscape context. Small, isolated woodlots composed largely of forest edge with high fruit and insect abundance may, therefore, be important conservation targets in highly fragmented landscapes where forest cover is limited.

[学科分类] 动物科学

[关键词] forest patches;habitat selection;migration;migratory landbirds;stopover habitat