The importance of core habitat for a threatened species in changing landscapes

1. Habitat loss, fragmentation and alteration of the landscape matrix are interdependent processes, collectively responsible for most recent species extinctions. Thus, determining the extent to which these landscape processes affect animals is critical for conservation. However, researchers have often assumed that interdependent effects are independently related to animals’ responses, underestimating the importance of one or several landscape processes in driving species declines. 2. We demonstrate how to disentangle the interdependent effects of habitat area, fragmentation, and edge context on population size by assessing abundance of a rapidly-declining grassland songbird species (Grasshopper Sparrow, Ammodramus savannarum) in eastern Kansas (USA). We conducted > 7,000 point-count bird surveys at > 2,000 sites over two breeding seasons, then modelled the direct, interactive, and indirect effects of landscape factors on abundance within spatial scales (200-, 400-, 800-, 1600-m r...