Waterfowl managers are concerned that Lesser Scaup (Aythya affinis) breeding populations remain below conservation goals. Contrasting population growth trajectories for sympatric, phylogenetically similar and Ring-necked Duck collaris) at Erickson, Manitoba, Canada, prompted investigations might help explain these trends provide insight management of both species. We collected data (2008–2018) ...

We report a negative correlation between the weight of a female convict cichlid, Cichlasoma nigrofasciatum, and the magnitude of her defence against a model brood predator for a brood reduced to 100 eggs. We account for this relationship by the fact that a larger female is more likely to spawn a larger number of eggs than is a smaller female, making a fixed number of eggs relatively less valuab...

Jacanas represent the extreme in avian sex-role reversal. We studied the division of labour between the two sexes in parental care of the eggs and chicks in wattled jacanas, Jacana jacana, in the Republic of Panama. Males were the sole incubators of the eggs (515 clutches). Males were also the sole caretakers of chicks for 97% of broods (NZ 252). Caretaking activities included continuous close ...

Competition between offspring can greatly influence offspring fitness and parental investment decisions, especially in communal breeders where unrelated competitors have less incentive to concede resources. Given the potential for escalated conflict, it remains unclear what mechanisms facilitate the evolution of communal breeding among unrelated females. Resolving this question requires simulta...

1. Polyembryonic parasitoid wasps in the family Encyrtidae (Hymenoptera) have evolved a caste system consisting of morphologically and functionally distinct larvae called soldiers and reproductives. 2. Two selective pressures are thought to underlie the evolution of the soldier caste: defence against competitors and resolution of the sex ratio conflict. Previous studies also indicate that soldi...

Because workers in colonies of eusocial Hymenoptera are more closely related to sisters than to brothers, theory predicts workers should bias investment in reproductive broods to favour reproductive females over males. However, conflict between queens and workers is predicted. Queens are equally related to daughters and sons, and should act to prevent workers from biasing investment. Previous s...

Abstract Patterns of extra pair paternity (EPP) and intraspecific brood parasitism (IBP) were studied in a Whiskered Tern Chlidonias hybrida population characterized by female desertion, high level courtship feedings (10%) low copulation (EPC; 0.6%). In this study, we used set microsatellite loci to analyse parentage 56 families from southern Poland. Depending on the method, detected that 1.4%–...

The female gastric brooding frog Rheobatrachus silus broods its young in its stomach. A substance that inhibits gastric acid secretion in a toad stomach preparation in vitro appears to be secreted by the developing young. This substance has been identified as prostaglandin E2. Rheobatrachus silus may thus have developed a mechanism whereby prostaglandin secreted by the larvae inhibits acid secr...

In mixed paternity broods, extra-pair offspring often perform better than their maternal half-siblings. This has been interpreted as evidence for genetic benefits of female promiscuity, but a new study shows that the difference in fitness may be largely due to a non-genetic, maternal effect.