Reid W V
Department of Zoology, University of Washington, 98195, Seattle, WA, USA.
Oecologia. 1987 Dec;74(3):458-467. doi: 10.1007/BF00378945.
Experimental enlargement of brood size in the glaucous-winged gull (Larus glaucescens) resulted in increased adult foraging time, decreased adult body weight at the end of the breeding season, and decreased over-winter adult survival. The decreased survival of breeding adults was associated with reduced body condition at the end of breeding (resulting from physiological costs of reproduction). Decreased survival was not due to an increased risk of injury or predation during the breeding season. Brood size did not directly affect the fecundity of surviving birds in the subsequent year. However, brood size may have an indirect effect on subsequent fecundity because the probability of mate loss increased among birds with large broods and the reproductive performance of birds with new mates was reduced. Based on estimates of life-time fitness calculated from fecundity and survivorship, birds with two- or three-chick broods (the normal brood size) have higher fitness than birds with one- or four-chick broods. However, the decreased fitness of birds with four-chick broods was slight, and probably not a sufficient explanation for the absence of natural four-chick broods in the glaucouswinged gull.
对灰翅鸥（Larus glaucescens）的巢雏数量进行实验性增加，结果导致成年鸥觅食时间增加、繁殖季节结束时成年鸥体重下降以及越冬成年鸥存活率降低。繁殖成年鸥存活率降低与繁殖结束时身体状况变差有关（这是由繁殖的生理成本导致的）。存活率降低并非由于繁殖季节受伤或被捕食的风险增加。巢雏数量并未直接影响次年存活鸟类的繁殖力。然而，巢雏数量可能对后续繁殖力有间接影响，因为雏鸟数量多的鸟类失去配偶的概率增加，且新配偶鸟类的繁殖表现会降低。根据从繁殖力和存活率计算出的终身适合度估计，育有两雏或三雏（正常巢雏数量）的鸟类比育有一雏或四雏的鸟类具有更高的适合度。然而，育有四雏的鸟类适合度下降幅度较小，可能不足以解释灰翅鸥自然状态下不存在四雏巢的现象。
