Mixed species nesting associations in a northeastern deciduous forest

Mixed species nesting associations (MSNA) occur when two or more species aggregate nests in space and time. In this study I describe nesting associations among songbirds breeding in forested habitat at Powdermill Nature Reserve in Western Pennsylvania, test if the distribution of nests correlates with habitat characteristics, and determine if MSNA impacts daily nest survival rates (DSR). I examined nesting associations involving Wood Thrushes (Hylocichla mustelina) and modeled DSR of thrushes. I also conducted artificial nest experiments in which I looked at the effects of density and nesting strata on nest survivorship. 65% of Wood Thrushes nested within 50 m of one to four other birds, and the nests were spatially aggregated. In contrast, only 15% of sites that lacked a Wood Thrush nest had 2 or more nests. Habitat characteristics including stem density and diversity were not correlated with the number of nests in an area. The best supported model of Wood Thrush DSR includes the interaction of time and number of nesting neighbors. DSR slightly decreased with increasing neighbor density. In three of the four artificial nest experiments, nest success decreased with higher nest density. In 2011, DSR decreased when nests were placed at different heights, but increased when nests were placed at the same height. MSNA are prevalent at Powdermill Nature Reserve, and birds do not aggregate nests around specific habitat features. However, daily nest survival is, in general, negatively affected by these associations, although these negative effects are marginal at low nest densities, such as those observed on the reserve. The question remains, then as to why these birds form these associations. One possibility is that adult survival is higher among birds in MSNA than among solitary nesters, or that other species in the association benefit from nesting near Wood Thrushes.Ph.D.Includes bibliographical referencesby Jean Elizabeth De