Extra-pair paternity in a species with frequent extra-pair courtship feedings, few extra-pair copulations, and male-biased parental care

Patterns of extra pair paternity (EPP) and intraspecific brood parasitism (IBP) were studied in a Whiskered Tern Chlidonias hybrida population characterized by female brood desertion, a high level of extra pair courtship feedings (10%) and a low level of extra pair copulation (EPC; 0.6%). In this study, we used a set of microsatellite loci to analyse parentage in 56 Whiskered Tern families from southern Poland. Depending on the method, we detected that 1.4%–3.6% of chicks were sired by an extra-pair male, and extra-pair chicks were present in 3.6%–8.9% of broods. IBP was observed in 8.9%–14.3% of broods, corresponding to 3.6%–6.4% of the chicks. The low rate of EPP is in agreement with the hypothesis that in species with high male parental investment, females should avoid EPC. The low level of IBP indicates that intraspecific egg dumping is not a common female strategy in Whiskered Tern, similar to many other colonial waterbird species.

Mating strategies, parental investment and mutual ornamentation in Iberian Rock Sparrows (Petronia petronia)

Relatively few bird species show complex social mating systems whose preponderance in a population is likely to affect the patterns of parental care observed there. In turn, parental investment is likely to be related to the expression of certain ornaments, which may reveal information on the bearer’s individual quality. Here we address both issues in a species characterised by several forms of parental care (both biparental and uniparental care) and in which both sexes possess a yellow breast patch, the rock sparrow (Petronia petronia). In our population, males contributed more to the care of the young in comparison with other populations. Social monogamy was the most frequent mating pattern and the percentage of cases of female (or male) brood desertion was lower with respect to that reported in previous studies, suggesting a flexible behaviour of this species to deal with different social environments. Birds did not pair assortatively with respect to the size of the yellow breast patch and we found no significant relationship between this trait and the frequency with which parents provisioned their chicks. However, we observed a positive relationship between male yellow patch size and nestling tarsus length, which suggests that more ornamented males are better parents. Males, but not females, differentially allocated parental investment in response to female ornamentation, although the benefits that males may gain from choosing more attractive females remain unidentified. Our results on paternal care investment along with previous studies on this species, reinforcing the view that the rock sparrow constitutes a good model to study sexual conflict over parental care under different social environments.

Breeding biology of Purple Sandpipers Calidris maritima on the Hardangervidda, southern Norway

Breeding Purple Sandpipers Calidris maritima were studied within an area of approximately 32 km2 on the Hardangervidda, southern Norway during 1978 to 1986. The minimum average density was 1.0 pairs per km2 in 1984. Clutch sizes were 3–4 (mean = 3.74), and egg sizes were small, reflecting the small size of the females compared to other populations. Hatching was in late June and clutch survival was 75%. The eggs in one nest were believed to have been trampled by a Reindeer. Chick growth was described for two broods. Broods were mostly attended by males. Only 8% (2 of 24 broods) were attended by females. Adult masses declined during the breeding season, supporting the theory that brood desertion by Arctic-breeding sandpipers could be related to loss of condition in the breeding adults. However, females, who usually desert the brood, did not decline in mass any faster than males. Birds from one pair were faithful to mate and site; the birds wintered apart (the female was seen in winter) and the pair re-united on the breeding territory.