Differences in rates of nest-visitation and removal of faecal sacs by male and female White-rumped Swallows

Abstract

Despite being a common and widespread species, the White-rumped Swallow (Tachycineta leucorrhoa) is one of the least-studied members of its genus. We examined the rates of nest-visitation and nest-sanitation of male and female White-rumped Swallows during the nestling period, in 23 nests, and compared them with those of the extensively studied Tree Swallow (Tachycineta bicolor). White-rumped Swallow pairs increased the rate of nest-visitation as nestlings grew older, as was found in Tree Swallows. Females made significantly more visits to the nest than males, and the asymmetry was maintained irrespectively of the age of nestlings. These results are similar to those reported from Tree Swallows in the eastern United States, but differ from the equality of roles found in Ontario, Canada. Female and male White-rumped Swallows removed faecal sacs at the same rate when nestlings were young (Day 4) but by Day 12 females had quadrupled their effort whereas the rate of sanitation by males remained constant. Overall, female White-rumped Swallows made a significantly larger parental investment than males (as measured by number of visits to nests and, thus, presumably rates of feeding, and in contribution to nest-sanitation) and, in this respect, the asymmetry in parental investment is greater than that reported for Tree Swallows.