Dr. Michael P. Lombardo


We extensively monitored the nests of Tree Swallows (Tachycineta bicolor) at 100 nest boxes every day during each breeding season from 1992 to 2006. The birds were banded and recorded as a means to track those who returned as recruits. We identified 166 recruits; the sex ratio of recruits was not significantly different from 50:50 and the distribution of recruits between nests was no different than expected by chance. We calculated a local recruitment rate of 4.79% when considering all nestlings (N=3463). We found a significant difference between brood size at hatching categories (1-3, 4, 5, 6, 7-8) and whether or not a recruit was produced (p<0.05). But this difference disappeared when limiting consideration to the most common brood sizes of 4, 5, and 6. Therefore the likelihood of producing a recruit is not influenced by family size across the most common brood sizes. We found a significant relationship between clutch initiation date and whether or not a recruit was produced for all nests (p<0.05). We suggest this to be an example of the “relative age effect.” We also found clutch size was negatively correlated with clutch initiation date (p=0.00). We found no significant effects of the mother’s age or physical characteristics of the parents on the likelihood of producing a recruit.