Ss. Sloan et al., DEPREDATION RATES AND PREDATORS AT ARTIFICIAL BIRD NESTS IN AN UNFRAGMENTED NORTHERN HARDWOODS FOREST, The Journal of wildlife management, 62(2), 1998, pp. 529-539
Spatial and temporal patterns of predation on birds' nests must be und
erstood to determine their effects on bird populations. We used artifi
cial bird nests containing Japanese quail (Coturnix japonica) eggs to
examine effects of forest strata (ground, shrub, subcanopy), time of s
eason (early vs. midsummer), and habitat (deciduous vs. mixed conifero
us-deciduous) on nest depredation rates in an unfragmented and relativ
ely undisturbed temperate forest in the White Mountains, New Hampshire
. We found that depredation rates differed significantly and most stro
ngly among forest strata (P < 0.002), with nests on the ground having
the lowest rate of depredation (31-46%) and those in the shrub layer h
aving the highest (73-88%). Seasonal and habitat variation were also e
vident, but no consistent trends were found between early and midsumme
r or between habitats. Depredation rates at artificial nests in shrub
and subcanopy strata were 2-3 times higher than depredation of real bi
rds' nests in those same strata in the same years. Using cameras at a
separate set of artificial nests on each plot, we identified 7 predato
r species, of which the red squirrel (Tamiasciurus hudsonicus) was the
most frequent in 1990 and the fisher (Martes pennanti) in 1991. Stati
stical and photographic evidence suggested that fisher in 1991 located
and depredated artificial nests systematically possibly by following
human scent. These results identify the importance of nest strata, sea
son, and composition of the predator community for the nesting success
of forest songbirds in large tracts of undisturbed forest, and emphas
ize several important potential biases in studies using artificial nes
ts.