AUTHORS: Paul Schilke*, Anna Pidgeon – Silvis Lab Department of Forest and Wildlife Ecology, University of Wisconsin-Madison
ABSTRACT: Flows of materials across ecosystem boundaries can be an important determinant of ecosystem structure. For example, food resources from aquatic ecosystems that move into adjacent terrestrial ecosystems can affect the abundance or density of terrestrial consumers such as birds. Increased numbers of insectivorous birds occur near rivers and streams due to inputs of emergent aquatic insect food resources. However, despite their prevalence in north-temperate and boreal landscapes, the effect of lake-derived food resources on forest bird populations has not been characterized. We asked whether the presence of lakes and the density of emergent aquatic insects were correlated with the abundance of forest breeding birds. We conducted bird point counts during three breeding seasons and captured emergent aquatic insects on sticky traps in nearshore and inland areas in the Northern Highlands Lake District of Wisconsin. We found that several insectivorous bird species, Eastern Kingbird, Eastern Wood-Pewee, and Yellow-rumped Warbler, were more abundant near lakes, but that bird abundance was not correlated with emergent aquatic insect density. Our results suggest that the presence of lakes is an important determinant of forest songbird community composition, but other factors, such as vegetation structure, may be more important than food inputs from aquatic ecosystems in determining bird community composition.
