Evol Ecol Res 5: 589-596 (2003)     Full PDF if your library subscribes.

Delayed maturation in birds in relation to social foraging and breeding competition

Guy Beauchamp*

Faculty of Veterinary Medicine, University of Montréal, PO Box 5000, St-Hyacinthe, Québec J2S 7C6, Canada

e-mail: guy.beauchamp@umontreal.ca


Delay in the achievement of adult appearance is common in many species of birds, but the adaptive significance of delayed maturation is unclear. Most adaptive hypotheses focus on benefits of honestly advertising youth and inexperience during the breeding or non-breeding season. Generally, delayed maturation in traits such as plumage is expected to be more prevalent in species that experience more competition for resources. I examined the association between delayed maturation and extent of competition in a large number of pairs consisting of closely related species with contrasting modes of maturation. The occurrence of delayed maturation increased in species that foraged in flocks rather than solitarily, supporting the hypothesis that competition for food during the non-breeding season is associated with the evolution of delayed maturation. Delayed maturation was more likely in dichromatic species, which are thought to experience more intense sexual selection, suggesting an association between delayed maturation and breeding competition. Delayed maturation was also more prevalent in cooperative breeders, but more often involved non-plumage traits, such as iris coloration, suggesting a cost to the use of plumage signals. As dichromatic species and cooperative breeders often flocked in the non-breeding season, the relative contribution of factors acting in each season remains to be established. However, the results suggest that the scope for factors acting alone in the breeding season is limited.

Keywords: birds, breeding competition, cooperative breeding, delayed maturation, flocking, pairwise comparative method, plumage dichromatism.

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