干旱区生态环境知识资源中心

The breeding effort of Arctic Terns Sterna paradisaea in two conditions of low food availability in Shetland (A: poor food supply during courtship and very poor during chick rearing, B: very poor during courtship and poor during chick rearing) was compared with that of Arctic Terns breeding in two areas of good food supply elsewhere. In Shetland situation B courtship prey were small and males provisioned females at a comparatively high rate. Neither the onset of laying nor egg size appeared to be affected; clutch size was slightly reduced in Shetland B, and a significantly higher proportion of birds deserted during incubation. Sandeels Ammodytes marinus were the main chick prey and feeding rates were highest when prey were small. No young fledged in the Shetland situations. Adults at the good food supply sites were heavier than those in Shetland and there was a significant positive relationship between adult weight at the time of hatching and the time to nest failure. These data are discussed in relation to the proximate role of food supply in influencing reproductive decisions and a model is proposed suggesting that individual Arctic Terns have a critical threshold body weight below which they abandon breeding.