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In cooperatively breeding species, group members may derive multiple benefits from helping to raise other individuals' offspring, yet not all individuals do so. In this study, we tested predictions from the "kin selection", "pay-to-stay", "group augmentation" and "skills" hypotheses, to explain why group members feed nestlings of breeding placid greenbuls (Phyllastrephus placidus). In our study population, about 70% of the breeding pairs were accompanied by subordinates, and in 60% of these cases at least one subordinate helped in provisioning nestlings. In total, 80% of the subordinates were related to one or both breeders. In accordance with the "kin selection" hypothesis, and contrary to the "pay-to-stay" hypothesis, all the helpers were first-order kin of the breeding female (although relatedness to the breeding male did not explain variation in helping) and the presence of helpers was associated with increased survival of the breeding pair. However, the propensity to help varied among group members, as 46% of group members related to the breeding female did not feed nestlings. Younger helpers fed offspring more often than older ones, supporting the "skills" and "group augmentation" hypotheses. However, support for the "group augmentation" hypothesis was mixed since subordinate sex and group size did not explain additional variation in helping propensity and effort. We argue that in addition to indirect and direct benefits, also the costs of helping as well as other types of helping aside from provisioning must be considered to better understand variation in helping behavior. [ABSTRACT FROM AUTHOR]

Socially monogamous females regularly mate with males outside the pair bond. The prevailing explanation for this behavior is that females gain genetic benefits resulting from increased fitness of extra-pair offspring. Furthermore, because of the risk of reduced paternal care in response to cuckoldry, females are expected to seek extra-pair copulations when they can rear offspring with little help from their social partner ("constrained female" hypothesis). We tested these hypotheses and analyzed variation in paternal care in the Afrotropical, facultative cooperative breeding placid greenbul (Phyllastrephus placidus). Overall, approximately 50% of the offspring resulted from extra-pair (and extra-group) mating. Identified extra-pair males were in most cases neighboring dominant males, yet never within-group subordinates. As predicted by the constrained female hypothesis, the occurrence of extra-pair paternity (EPP) increased with the number of cooperative helpers (and not with total group size). However, dominant males did not adjust their food provisioning rates in response to EPP. Although extra-pair males were more strongly related to the dominant female and less heterozygous than the latter's social mate, this did not result in more inbred extra-pair offspring, likely because identified extra-pair males were not representative of the extra-pair male population. While earlier studies on EPP mainly focused on male genetic quality, results from this study provide evidence that female's social context may affect extra-pair strategies too. [ABSTRACT FROM AUTHOR]

The article focuses on the mechanisms of vulture coexistence and its pattern of abundance in Masai Mara National Reserve, Kenya. It states that the species are associated on the basis of similar dietary needs and morphology of beaks and they rarely show the degree of disassociation. The findings suggests that the changing land use in Mara ecosystem can lead to ungulates reduction which in turn, can adversely affect social vultures.