Heterochrony, deferred breeding and avian sociality.

Abstract

Heterochrony refers to changes in the timing of ontogeny. Progenesis is the acceleration of sexual development with respect to somatic maturation; neoteny is the retardation of somatic development with respect to sexual maturation. Examples of breeding by morphologically subadult birds are given: it is crucial to establish whether specific causes of delayed somatic maturation truly represent delayed sexual maturation or reflect situations in which intensive intraspecific competition in highly social species has favoured retention of juvenile characters and deferred breeding in sexually mature individuals. Attention is focused on Corvidae as an example of a group where social behaviour is important. Relations between female mimicry, crypsis and neoteny are examined. Means are discussed of testing predictions about those ecological conditions under which paedomorphosis may be expected. -P.J.Jarvis