Aquatic Community Characteristics Influence the Foraging Patterns of Tree Swallows

During periods of inclement spring weather, Tree Swallows (Tachycineta bicolor) were observed foraging close to the surface of a series of experimentally manipulated ponds. Censuses of foraging swallows during these periods indicated that the use of ponds for foraging was positively affected by earlier additions of nutrients and the removal of fish from the ponds. Collections of emerging insects from these ponds indicated that nutrient additions and the removal of fish greatly increased the numbers of insects emerging from those ponds. The ability of Tree Swallows to exploit local concentrations of food may be critical to their ability to return to the breeding grounds before aerial insects are reliably available.