| Summary: | The vertical structure and composition of vegetation can influence the quantity and quality of potential nesting sites for birds. Interspecific competition for high-quality nesting habitat may force some individuals into suboptimal habitat and lead to reduced reproductive success, eventually leading to changes in distribution or abundance. Large climate-mediated shifts in vegetation, including the rapid expansion of shrubs onto tundra, are occurring in the Arctic across important breeding grounds of many shorebird species of conservation concern. We investigated effects of vegetation structure and composition on nest-site selection and nest success of sympatrically breeding American Golden-Plovers (Pluvialis dominica) and Pacific Golden-Plovers (P. fulva), which nest along an elevational gradient ranging from coastal tundra meadows to alpine tundra. Both species strongly selected nest sites with less cover of tall shrubs and other tall vegetation than available at random sites within their territories. American Golden-Plovers selected territories and nest sites that were higher in elevation and had more rocky substrates and less graminoid vegetation than those selected by Pacific Golden-Plovers. The daily nest survival rate was equivalent in the 2 species (0.966, 95% CI: 0.955, 0.975) and similar to that found in other Arctic-breeding shorebirds; however, contrary to predictions, nest survival was not associated with habitat features selected for nest sites for either species. Strong selection of open habitat for nest sites suggests that continued climate-related shrub expansion may reduce the amount of suitable breeding habitat for both species, but partitioning along the elevational gradient and differences in body size suggest that impacts may be more severe for Pacific Golden-Plovers. Additional research is needed to determine if differential selection of nesting habitat is related to survival of the adults or their young.
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