Birds of Indian Subcontinent

Breeding biology, sexually dimorphic development and nestling testosterone concentrations of the classically polyandrous African black coucal, Centropus grillii

Publication Type:Journal Article
Year of Publication:2005
Authors:Goymann, W, KEMPENAERS, BART, Wingfield, J
Journal:Journal of Ornithology
Date Published:2005
ISBN Number:2193-7192
Keywords:Centropus, Centropus bengalensis, Centropus grillii, Centropus sinensis, Cuculidae
Abstract:Many internal and environmental factors influence the growth of birds. Here we ask whether the reversed sexual dimorphism in the classically polyandrous black coucal is reflected in differential growth and fledging parameters of females and males. We also investigate whether androgen concentrations were higher in females than males during the nestling development, thus, providing a potential mechanism for the ‘behavioural masculinization’ of female black coucals. Furthermore, we give a detailed description of the breeding biology of this little studied and unusual bird species. Black coucal eggs were smaller, and the incubation and nestling periods were shorter than expected for a bird of that size. In absolute terms female black coucals grew faster than males and left the nest with a larger body mass, suggesting that females are the more expensive sex to rear in this species. However, in relation to adult body size, females grew slower and reached a smaller proportion of their adult body size than males upon fledging. ‘Testosterone’ concentrations were significantly higher in male than in female nestlings, hence not supporting a role of circulating androgens in the ontogeny of sex-role reversal. To our knowledge, the early sex differences in ‘testosterone’ levels of black coucals represent the first evidence that such differences exist in nestlings of altricial birds. We present anecdotal evidence that the differences may be related to an early maturation of male reproductive organs in black coucals. In females but not in males, ‘testosterone’ concentrations were related to structural growth rates.
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith