title: Endocrine correlates of the breeding asynchrony between two Corsican populations of blue tits (Parus caeruleus).
abstract: Analyses of the development of the reproductive system in seasonally breeding birds in the framework of long-term ecological studies are rare. Here, we present the first results of such a study in two Corsican populations of a European passerine bird, the blue tit (Parus caeruleus). The two study populations occupy different oak habitats and are separated by only 25 km. Despite their close proximity, they show a one-month difference in onset of egg laying, even after controlling for altitude. This micro-geographic difference in breeding date appears adaptive because both study populations raise chicks when food is most plentiful. In our study, males reached their maximum song activity during the egg-laying stage while maximal testosterone levels and testes sizes were reached 2-3 weeks before egg laying. The rate of development of the reproductive system in males was much faster in the earlier population, in spite of a similar onset of gonad development and song activity for the two study populations. No change in the volume of the song-control nuclei (HVC and RA) could be detected during the study period. Development of brain nuclei was completed 2-3 months before the beginning of intense sexual activity.
authors.affiliation: Center for Cellular and Molecular Neurobiology, Research Group in Behavioural Neuroendocrinology, Univ. of Liège, 17 Place Delcour (Bât. L1), B-4020 Liège, Belgium.
authors.forename: Samuel P
authors.initials: SP
authors.lastname: Caro
authors.forename: Jacques
authors.initials: J
authors.lastname: Balthazart
authors.forename: Donald W
authors.initials: DW
authors.lastname: Thomas
authors.forename: André
authors.initials: A
authors.lastname: Lacroix
authors.forename: Olivier
authors.initials: O
authors.lastname: Chastel
authors.forename: Marcel M
authors.initials: MM
authors.lastname: Lambrechts
mesh_terms: D000818:Animals; D001921:Brain / Q000254:growth & development; D004777:Environment; D005260:Female; D005602:France; D008297:Male; D010053:Ovary / Q000254:growth & development; D012098:Reproduction / Q000502:physiology*; D012621:Seasons; D020308:Songbirds / Q000502:physiology*; D013737:Testis / Q000254:growth & development; D013739:Testosterone / Q000097:blood / Q000494:pharmacology*; D013997:Time Factors; D014828:Vocalization, Animal
chemical_list: D013739:Testosterone