Dj. Flaspohler et al., Species-specific edge effects on nest success and breeding bird density ina forested landscape, ECOL APPL, 11(1), 2001, pp. 32-46
Using natural nests of eight bird species, we provide one of the first mult
ispecies tests for edge effects on reproductive success in a forested lands
cape. Our primary objective was to assess whether distance to the edge of r
ecent clearcuts was related to nesting success in intact northern hardwood
forests. Estimated nest success was generally lower for the two ground-nest
ing species than for the six canopy-nesting species. Brood parasitism was <
3% for species which typically accept eggs of the Brown-headed Cowbird (Mol
othrus ater), and nest predation was the most common cause of nest failure.
Probability of nest failure was influenced by distance to forest edge for
the ground-nesting Hermit Thrush (Catharus guttatus) and Ovenbird (Seiurus
aurocapillus), but not for six canopy-nesting species. For the Hermit Thrus
h and Ovenbird, nest success relative to decreasing distance to the edge wa
s reduced during the nestling stage, but not the incubation stage. Nest den
sity appeared to be higher in forest zones near the clearcut edge for groun
d-nesting and for several canopy-nesting species. Our data suggest that the
effect of proximity to edge on nest success for ground-nesting species may
penetrate 300 m into intact forest, while the effect of proximity to edge
on nest density may penetrate farther. These data suggest that the creation
of openings in forested landscapes reduces nest success and increases nest
density for some species of migratory birds in a zone adjacent to the open
ing. This pattern supports the notion that "ecological traps" may exist for
ground-nesting birds in areas near recently created forest openings. Becau
se areas of contiguous forest (e.g., publicly owned forest) in the Upper Gr
eat Lakes remain relatively intact, they may serve as source habitat for re
gional songbird metapopulations.