Griesser, Michael
- Uppsala University
Abstract
A large number of bird species live in stable groups, and this sets the scene for complex social behaviours, such as cooperative breeding. The vast majority of groups consist of families which arise when young postpone dispersal and remain with their parents beyond independence. However, the factors selecting for the evolution of families and thus also cooperative breeding among birds, are still a challenging puzzle. The currently accepted key explanation for the evolution of families and cooperative breeding focuses on dispersal constraints. While constraints successfully explain within-population dispersal decisions, they fail as an ultimate explanation because offspring in the majority of species face some sort of dispersal constraint, yet still disperse promptly. Recent alternative explanations focus on the role of philopatry and nepotism, and emphasise a key role of life-history for the evolution of families. Phylogenetic analyses and field studies have indicated that living in family groups is far more widespread among long-lived species than short-lived ones. A long lifespan gives parents the opportunity to invest in their offspring for a prolonged period, while this option is less viable for short-lived species. Thus, living with nepotistic parents provides offspring with direct fitness benefits that can select for the evolution of family living beyond independence. Nevertheless this generalisation is brought into question since many long-lived bird species do not live in family groups. An alternative approach attempts to explain family living through the variation in territory quality. Here the incentive to remain with the parents is created by the availability of resources on the natal territory independent of parental nepotism. However, there is not only cooperation, conflicts are also common place in families. Living with independent, sexually mature offspring can lead to conflicts through a change in resource availability or the death of a parent. Therefore families can be expected to be dynamic societies where both parent and offspring decisions depend on each other, and family maintenance depends upon the current ecological conditions. Based on this background, here we review recent studies that have investigated the processes that facilitate family formation, and which highlight both cooperation and conflict that arises from living in family groups. We examine the strengths of current models and explore ideas for a more coherent framework in which to understand prolonged family association in birds. We argue that two paths lead to family living, depending on the life-history. In medium-short lived species where the postponement of independent reproduction comes at a high cost, offspring can benefit from an association with their parents until the next breeding season. In longer-lived species, offspring actually benefit from postponing the onset of independent reproduction, making family living beyond the first year of life an adaptive strategy, and giving the option for cooperative breeding. These processes are illustrated by 5 species-specific case studies. We then finally suggest a number of key questions to developing a deeper understanding of the evolution of family living in birds. © 2010 Nova Science Publishers, Inc. All rights reserved.
Published in
Title: New Research in Behavioral and Chemical Ecology
Publisher: Nova Science Publishers
SLU Authors
UKÄ Subject classification
Environmental Sciences and Nature Conservation
Publication identifier
- ISBN: 978-1-60741-099-7
Permanent link to this page (URI)
https://res.slu.se/id/publ/26880