Temporal variation in annual survival probability of the Eurasian woodcock Scolopax rusticola wintering in France

Abstract

International audienceLebreton, J-D. 2002: Temporal variation in annual survival probability of the Eurasian wood-cock Scolopax rusticola wintering in France.-Wildl. Biol. 8: xxx-xxx. The Eurasian woodcock Scolopax rusticola is an important quarry species hunted all over its range. Some authors have reported local declines in both wintering and breeding woodcock numbers. In order to investigate whether these possible declines are the result of a negative trend in survival, we analysed 3,312 recoveries of 15,839 woodcocks ringed in France during 14 consecutive winters (1984/85-1997/98). We distinguished between winter (October-February) and summer (March-September) recoveries in order to estimate survival and recovery rate separately for each period because selective pressures during these two periods are likely to be different. Survival varied according to year during both winter and summer. Winter survival probability covaried positively with mean winter nocturnal temperature and ranged from 0.74 (SE = 0.057) during the winter of 1985/86 to 0.83 (SE = 0.042) during the winter of 1994/95. Mortality of first-year birds was 22% higher than that of adults in any year. Results from a second analysis in which we compared survival of birds ringed during 1991-1997 in the three main woodcock wintering areas along the French Atlantic coast suggested a threshold effect of weather conditions. Mean winter survival covaried with temperature and rainfall mainly in the northernmost regions where weather conditions are more severe. We did not find any particular trend in survival probability that could explain the possible declines in woodcock numbers. However, the generally low adult annual survival, and the negative influence of stochastic events such as severe winter conditions might drive populations to a level from which it would be difficult to recover. Results of a two-age-class demographic model are discussed together with implications for management