This paper deals with species thought to be permanent residents in southern New England. However, although the species are present year-round, the same individuals are not necessarily present. In fact, overall densities as well as population distributions may change considerably between seasons. In a number of instances, short distance migrations occur. The full abstract of the paper follows:
Abstract. I studied 10 permanent resident bird species in unfragmented forests of eastern Connecticut to discover: 1) are populations of resident species truly sedentary or do they seasonally change in density and distribution and 2) are any seasonal changes in species’ occurrences related to environmental parameters in manners that help to explain the changes? I performed duplicate surveys using the variable circular plot technique at 50 systematically placed transects and characterized habitats at 15 plots/ transect. I related population densities to habitat features and also compared the occurrence of individual birds within habitat plots to the characteristics of those plots. The Tufted Titmouse (Poecile bicolor), Blue Jay (Cyanocitta cristata) and Northern Cardinal (Cardinalis cardinalis) showed consistent, significant population declines, whereas the Black-capped Chickadee (P. atricapillus) showed significant increases from summer to winter and the Red-bellied Woodpecker (Melanerpes carolinus) had nearly significant winter increases. Five species had no clear seasonal trend. Populations of six of 10 species became significantly more concentrated from summer to winter at lower, more southerly elevations. Evidence for the association of species with aspects of habitat structure was limited regardless of the scale used to examine such associations. The lack of strong structural habitat associations may be expected among species often thought of as being ecological generalists, although findings also demo nstrated that the importance of structural features was not annually consistent, perhaps because these features varied in their annual importance. Despite observed population shifts by most resident species, including those thought to be largely sedentary, the principal factor related to seasonal population changes was wintering at lower, southerly elevations. Because elevation and latitude are strongly related inversely to average temperature in Connecticut, winter movements are likely driven by populations seeking less metabolically costly landscapes.