Lepage Denis, Gauthier Gilles, Reed Austin
Département de biologie and Centre d'Études Nordiques, Pavillon Vachon, Université Laval (Québec), G1K 7P4, Canada, , , , , , CA.
Canadian Wildlife Service, Environment Canada, 1141 route de l'Église, C.P. 10100, Ste-Foy (Québec), G1V 4H5, Canada, , , , , , CA.
Oecologia. 1998 Apr;114(2):226-235. doi: 10.1007/s004420050440.
Even though growth rate is an important fitness component, it is still controversial to what extent parent birds adjust the timing of offspring hatch to natural variations in food supply to maximize offspring growth. We studied the role of food availability in explaining inter- and intra-seasonal variation of growth rate in goslings of greater snow geese over 5 years. The peak of hatching generally coincided with the peak of food availability. However, early-hatched goslings usually grew faster than birds hatched at the peak, which in␣turn grew faster than late-hatched goslings, although this phenomenon was not observed in all years. There was considerable variation in growth rate among the five years, the smallest goslings produced in the best year (1991) being larger than the largest goslings of the poorest year (1994). We developed three indices of food availability, based on the cumulative availability of plant biomass and nitrogen content during the growth period, and showed that the cumulative exposure to nitrogen biomass explained up to 43% of variation (intra- and inter-annual) in body size just before fledging. In years with good feeding conditions, early-hatched goslings had access to more nitrogen during their growing period than those hatching on or after the peak and they grew faster. In years of lower food availability, early-hatched goslings had no detectable advantage over peak- or late-hatched birds for access to protein-rich food and no seasonal decline in growth rate was observed. These results confirm the critical role of food supply in the seasonal variation of growth rate in Arctic-nesting geese.
尽管生长速率是一个重要的适合度组成部分，但亲鸟在多大程度上根据食物供应的自然变化来调整后代孵化时间以实现后代生长最大化，这一点仍存在争议。我们研究了食物可获得性在解释5年里大雪雁雏鹅生长速率的季节间和季节内变化方面所起的作用。孵化高峰期通常与食物可获得性的高峰期相吻合。然而，早孵化的雏鹅通常比在高峰期孵化的雏鹅生长得更快，而高峰期孵化的雏鹅又比晚孵化的雏鹅生长得更快，不过并非在所有年份都观察到这种现象。这5年中生长速率存在相当大的差异，在最佳年份（1991年）出生的最小雏鹅比最差年份（1994年）出生的最大雏鹅还要大。我们根据生长期间植物生物量和氮含量的累积可获得性制定了三个食物可获得性指数，并表明在离巢前氮生物量的累积暴露解释了高达43%的（年度内和年度间）体型变化。在食物条件良好的年份，早孵化的雏鹅在生长期间比在高峰期或高峰期之后孵化的雏鹅能够获取更多的氮，并且它们生长得更快。在食物可获得性较低的年份，早孵化的雏鹅在获取富含蛋白质食物方面相对于高峰期或晚孵化的雏鹅没有明显优势，并且未观察到生长速率的季节性下降。这些结果证实了食物供应在北极筑巢鹅生长速率的季节性变化中所起的关键作用。
