Figure 2.

Breeding-colony size rank (mean ±SEM) chosen by cross-fostered cliff swallows of each sex in 1997 (a and b) and 1998 (c; sexes combined) in relation to rank of colony in which a bird was born and reared. The same rank for birth and rearing colonies are for control individuals that were not cross fostered. The numbers above bars (sample sizes) indicate number of birds from each treatment recaptured as breeders. Within each year, bars with the same letter denote means that did not differ significantly (Wilcoxon test, P > 0.10); bars with different letters denote means that differed significantly (Wilcoxon test, P ≤ 0.05). A two-way ANOVA revealed that birth–rearing colony combination had a significant effect on breeding-colony rank (F = 10.85, P < 0.001), but neither sex alone (F = 0.05, P = 0.82) nor an interaction between sex and birth–rearing colony (F = 0.69, P = 0.72) was significant.