Ring-billed gull (Larus delawarensis) egg colour, egg dimensions, egg shape, egg-laying intervals, nest initiation dates, and fertility were documented at several different colonies over a 6-year period. Significantly greater variability in egg dimensions and egg shape, lower fertility, and atypical laying intervals in mixed-coloured clutches compared with even-coloured clutches suggest that more than one female laid eggs in mixed-coloured clutches. We present evidence that some odd-coloured eggs were laid by females that parasitized nests.
AbstractExtrapair paternity and its correlates with breeding synchrony were examined in Gadwall (Anas strepera) using microsatellite DNA fingerprinting. Eleven of 261 ducklings (4.2%) within 8 of 29 broods (27.6%) had genotypes consistent with extrapair fertilizations, a comparable frequency to other species of waterfowl for which extrapair paternity has been documented. We found no evidence of intraspecific brood parasitism. The frequency of extrapair paternity was not significantly correlated with breeding synchrony. We suggest that female absences during egg-laying may have provided males with opportunities to pursue extrapair copulation when breeding was synchronous.
Genetic evidence of extra-pair paternity and intraspecific brood parasitism in the monk parakeet
