Habitat Selection by American Redstarts along a Successional Gradient in Northern Hardwoods Forest: Evaluation of Habitat Quality

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TO investigate the possible relationship between habitat changes and popu- lation declines in the American Redstart (Setophaga ruticilla), I studied redstart population structure in habitats spanning a successional gradient in northern hardwoods forests of the White Mountains, New Hampshire during the summers of 1992 to 1994. Early successional stands, in general, supported higher densities and a greater percentage of older (ASY) males than did mature stands. Among mature forests, redstart densities and proportions of ASY males were lower in stands with greater representation of conifers. Mating success varied among habitats, primarily for yearling males, which were more likely to obtain a mate in the early successional habitats and less likely to do so in coniferous habitats. Territories were significantly smaller in early successional habitats. The combination of high densities, high proportions of older males, high mating success in yearlings, and small territory size supports the hypothesis that early successional habitats are more suitable for redstarts than are older forests. Early successional habitats may be more suitable due to higher prey availability and/ or reduced predation on nests, although conclusive data are not available for either of these variables. If reproductive success follows a similar pattern, then the loss of early successional habitats as a result of reforestation in the breeding areas could be a major cause of population declines of American Redstarts in New England. Received 18 December 1995, accepted 8 May 1996.