Cooperative Breeding. How environment and life history correlate to cooperative breeding in birds

Resumen o Introducción

Cooperative breeding systems, in which the offspring of a species is raised and nurtured by not only the parental individuals, but also by alloparents, are widespread among social animals. In birds, around 9 % of all species engage in cooperative breeding. The question why an individual engages in cooperative breeding instead of breeding independently has been a continuous point for researchers.

The fitness benefits that an individual gains from cooperative breeding differ from inclusive fitness in the Florida Scrub Jay to a rise of available food sources and group benefits for the Azure-Winged Magpie and Brown-headed Nuthatch. Since the graphic distribution of cooperative breeding in birds is highly variable, it has been suggested that ecological conditions must play a part in what drives cooperative breeding. The ‘Hard-Life Hypothesis’ states that the more barren the environment in which a species has to raise their offspring, the more likely it is that the individuals will participate in cooperative breeding. The ‘Ecological-Constraint Hypothesis’ states that, if an individual cannot find an own habitat due to saturation of the surrounding territories, it will stay and act as an alloparent for its relatives instead. Other, more recent theories take the life history into account as well, stating that the survival rates of not only the offspring but all group members of the system rise.