Least Flycatcher nest success increases at sites with extensive northern hardwood cover at the landscape scale

The Least Flycatcher (Empidonax minimus), a small migratory songbird, has experienced significant population declines across its North American range over the past five decades. Whereas the causes of this decline remain complex and multifaceted, habitat loss, fragmentation, and changes in forest composition on the breeding grounds are suspected to play a critical role. To better understand the relationship between breeding habitat and reproductive success, we estimated nesting success across a gradient of increasing forest cover, i.e., 46% to 85%, at seven sites in Minnesota. Data from 171 nests revealed substantial variation in nesting success, ranging from 37% at the site with the lowest forest cover to 94% at the most forested site. Nesting success was significantly higher in landscapes dominated by northern hardwood forests, particularly those with abundant sugar maple (Acer saccharum), and in nests located lower in the canopy. These findings suggest that forest composition and landscape-scale forest cover are important predictors of reproductive success in Least Flycatchers. Although limited to a single breeding season, this study contributes to our understanding of the species’ breeding ecology and the importance of extensive northern hardwood forest, especially of mixed-age sugar maple and paper birch (Betula papyrifera), at both local, i.e., 100-m, and landscape, i.e., 10-km, scales.