Sexual precocity of European quail (Coturnix c. Coturnix) wintering in Portugal
La sexualité précoce des populations hivernantes de cailles des blés (Coturnix c. coturnix) au Portugal
Résumé
Quails issued of migrant parents show a large variability of their reproductive phenotypes when exposed in captivity to a winter Sahelian photoperiod (16º lat. N.). Fifteen per cent of these females lay spontaneously in December and/or January; 75% before late April. In order to evaluate the possibility of this sexual precocity in natural conditions, we have measured the gonadal development and other sexual characteristics: song, cloacal development, pair formation of the European quail (Coturnix c. coturnix) populations wintering in the alluvial plains in the Centre (39-40º lat. N.) of Portugal. The study was based on samples of birds shot there during the hunting seasons (September to December) of 1991, 1992, 1993 and 1994 (n=149). Results indicate that these wintering populations are starting their sexual development in late autumn. Importance and chronology of this sexual precocity seem to be related with sex: males were sexually more advanced than females. Distinct results were obtained in different years and stations according to weather conditions (temperature): in December 1992 (cold winter) only 38% of the birds analyzed in the coastal stations showed a beginning of sexual development, in contrast with 88% observed in December 1994. A large proportion (46% males, 51% females) of the birds shot on coastal stations (any frozen day) showed signs of sexual precocity (more than 100 mg of gonadal weight). Only a few birds were concerned the same year in colder interior stations of Centre Portugal as Guadiana basin (0% males and 18% females).
Comparision with previous results obtained for Morocco and Portugal allows us to say that the European quail seasonal cycles are similar in both North African and Iberian areas. Those wintering birds, probably "short migrants", are precocious March breeders, which means that in mild winter, they can initialize their sexual development as early as December.
These results justify the need of a wise protection of the quail present in December in some Portuguese agrosystems. Such conservative measures could have interesting consequences on the kinetics of all the Atlantic quail population.