• Weatherhead, Patrick J.


Fecal sac removal by Tree Swallows (Tachycineta bicolor) was monitored for 10 "land" nest boxes (> 100 m from water) and 13 "water" nest boxes (adjacent to or over water). The mean distance from the nest at which "land" birds dropped fecal sacs was more than double that for "water" birds. Departure directions for birds carrying fecal sacs were more variable than for birds not carrying fecal sacs although, contrary to prediction, "land" birds were not more variable than "water" birds. Combining data on the removal rate and weight of fecal sacs over the nestling period produced the estimate that for each nestling, parents removed 70 g of feces in 168 trips. It is hypothesized that where predation pressure requires more time and energy to be spent in disposing fecal sacs, clutch size will be smaller.