Fig. 1. Aerial views of the field sites indicating locations of hives (H) and feeders (F). White arrows are 200 m long and indicate the bees' outward flights to the feeders. North is indicated by black arrowheads. The agricultural fields adjacent to the treelines sloped downward away from the treelines; adjacent contour lines are separated by 6.1 m of elevation. Different sites served as donor and recipient sites in different experiments. The north-facing treeline (A) is at 75°47'12.1'W, 40°37'6.4'N, and the south-facing treeline (B) is at 75°47'12.6'W, 40°36'56.7'N.