Effects of group-selection opening size on the distribution and reproductive success of an early-successional shrubland bird

Group-selection is a widely used silvicultural technique, and although recent studies have compared the ecology of birds inhabiting patches of regenerating forest created by group-selection with that of birds in clearcuts, little is known about the effect of opening size and shape on the ecology of early-successional shrubland birds within stands treated with group-selection. We studied chestnut-sided warblers (Dendroica pensylvanica), which are an early-successional shrubland bird, nesting in 29 patches of regenerating (4–5 years old) northern hardwoods forest 0.15–0.69 ha in area to determine whether the ecology of this species is affected by patch size or shape. Chestnut-sided warbler density decreased with patch size, however nests were initiated earlier in larger patches. There were no relationships between patch area and number of young fledged per territory or nest predation rates. Similarly, there were no relationships between patch shape (defined as the ratio of the patch perimeter to the perimeter of a circle of the same area) and territory density, date of initiation of first nests, number of young fledged per territory, or nest predation rates. These results contrast with the results of studies of area sensitivity of mature forest and grassland birds, in which bird density is negatively related to patch area. However, later nest initiation in smaller patches suggests that smaller patches are lower quality habitat, which is consistent with the negative relationships between patch area and habitat quality reported in studies of birds nesting in patches of mature forest.