Habitat selection by migratory bird species affects their fitness. Studies of populations with marked individuals of known reproductive performance provide the greatest insight on the relationship between a species and the range of habitats it occupies. Canada Warblers (Wilsonia canadensis) have not been intensively investigated at the population level, despite significant regional declines in their numbers over the past 40 years (e.g., 4.6% year−1 in New Hampshire). We mapped 92 male territories over four years and quantified habitat structure and habitat composition for territories and nonterritory areas. Analyses revealed more shrubs (stems and foliage), more perch trees, and lower canopy height on territories. Birds returned at an average rate of 52.0 ± 2.96% (SE) and exhibited average between-year shifts of 32 m in territory locations. Over the four years, males had high pairing success (91.0 ± 5.61%). Three-quarters of paired males fledged at least one young. Pairing and fledging success did not influence site fidelity. Paired males had more shrub stems and song-perch trees. Territories of earlier-arriving males had more shrub stems. The high proportion of males pairing and successfully fledging young, together with the high average return rates, indicate that areas with dense subcanopy vegetation constitute prime Canada Warbler breeding habitat in New Hampshire. Timber harvest practices that result in high shrub density and residual standing trees, such as deferment or two-age harvest, have the potential to slow Canada Warbler population declines, but only if they are widely applied in forest management.
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