In behavioural sciences cooperation is considered an interaction between individuals of the same species, which is beneficial for the recipient but costly for the actor. The El Oro Parakeet (Pyrrhura orcesi) is a cooperatively breeding species, which means that one or more helpers assist in raising the young of a dominant breeding pair. Regarding the evolution of cooperative breeding, the question is whether helping has indeed positive fitness effects and if so whether only breeders or also helpers benefit from cooperation. My research focuses on fitness implications of individual variation within and among helpers and the identification of factors shaping the cooperative breeding system of the El Oro Parakeet. Considerable variation in group composition and helper contributions is the reason why this species is particularly suitable to address several hypotheses on the evolution and significance of variability in cooperative systems.
1. Causes for the variability in the breeding system and individual differences between helpers
The El Oro Parakeet is facultatively cooperative, so the crucial questions are why some individuals postpone own reproduction and act as helpers instead, and why the contribution of helpers shows considerable variation. I will evaluate different factors which could influence the decision of an individual, including body condition, relatedness, social interactions and personality traits such as consistency of behaviour over several years.
2. Consequences of the variability in cooperation for breeders and helpers
Costs and benefits of helping may vary for breeders and helpers depending on the participation of other group members in feeding the hatchlings. I will collect data on direct and indirect fitness traits over several years to investigate whether variability in helping behaviour can be explained by the unequal benefits that individuals can expect and whether helpers adjust their behaviour according to changes in the social structure and composition of their flocks.
3. The social structure of the groups and its implications for the development and maintenance of the cooperative breeding system
The social status of an individual in a group or population is often difficult to characterize, because it is determined by a complex set of behavioural interactions. I will use methods of the social network theory, which is more and more used to characterise animal societies, as a statistical framework for modelling the social population structure of the El Oro Parakeet. With these methods I aim to identify social characteristics favouring the evolution of cooperation in this species.
4. Conservation of the El Oro Parakeet
I will investigate genetic population differentiation and gene flow between populations in several forest fragments to understand the parakeet’s response to habitat fragmentation and thus provide a scientific background for the conservation measures which are currently being planned for this species.
The El Oro Parakeet is a globally endangered species with less than 1000 individuals that is endemic to the highly fragmented montane cloud forest of SW Ecuador. It is restricted to a narrow area of about 750 km² at an elevation of 600 to 1300 m. The effective population size is considerably lower due to the cooperative breeding system of the species with only a small percentage of adult birds reproducing each year.