Egg and seed removal at urban and suburban forest edges

Abstract

Predation rates of natural and artificial bird nests in rural landscapes have been the subject of numerous studies, often in the context of proximity to edge. Similar studies in urban and suburban landscapes are lacking. We carried out a study of egg and seed removal at forest reserve edges in three urban and two suburban forests in and near New York City in 1994-1995. Few significant edge effects were found, but this may have been because of the extraordinarily high rates of egg and seed removal. Daily removal rates were higher in suburban sites (eggs, 86%; seeds, 95%) than in urban sites (eggs, 64%; seeds, 88%). Exposed seeds and eggs suffered higher rates of removal than seeds and eggs covered by leaf litter. Despite statistically significant differences among treatments, all of these rates would be prohibitively high if experienced by ground-nesting birds or large-seeded trees (if removal was associated with predation). A survey of the literature suggests that egg predation rates are prohibitively high in cities and peak in suburban sites (at least in this study), then drop rapidly in ex-urban and rural sites, perhaps because of a similar pattern in the abundance of corvid bird predators.