The importance of egg hatchability and nest predation in clutch size evolution in altricial birds
The importance of egg hatchability and nest predation in clutch size evolution in altricial birds
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蛋孵化率和巢捕食在晚成鸟窝数进化中的重要性
作者：
S. Lundberg
作用于鸟类后代的所有不同死亡因素可根据其作用水平大致分为两类。首先，有个别蛋和雏鸟的死亡，第二，整个窝的破坏。后一种情况下的卵死亡通常是由于捕食，而前一种情况下的卵死亡则是由于卵的不育或胚胎的过早死亡。由于饥饿的死亡率发生在个别鸡的水平，其强度被认为是正相关的窝卵数。因此，通常会有一个最具生产力的育雏大小。当在一个模型中同时考虑蛋的孵化率和捕食时，会出现三种可能性：（1）最佳窝卵大小可能等于最具生产力的育雏，（2）当每日捕食风险很高时，可以减少窝卵大小。结果表明，捕食可能是一个更重要的决定因素离合器大小的演变比已普遍赞赏。(3)当每天被捕食的风险较低时，可能会进化出补偿产卵。后一种适应有利于不育卵的高发生率，而前一种适应有利于低发生率。粮食供应的增加可能导致这两种结果，这取决于鸡蛋死亡的发生率。
All the different mortality factors acting on avian offspring can roughly be divided into two groups with respect to their level of action. First, there are deaths of individual eggs and nestlings, and, second, the destruction of entire clutches. Deaths of eggs on the latter level is often due to predation and deaths on the former to infertility of the eggs or early deaths of embryos. Mortality due to starvation occur on the individual chick level, and its intensity is assumed to be correlated positively to clutch size. Therefore, there will generally exist a most productive brood size. When egg hatchability and predation are considered together in one model three possibilities arise: (1) the optimal clutch size may equal the most productive brood, (2) clutch size reduction is possible when the daily risk of predation is high. It is shown that predation potentially is a more important determinant of clutch size evolution than has been generally appreciated. (3) Compensatory egg laying may evolve when the daily risk of predation is low. The latter adaptation is favoured by a high incidence of infertile eggs and the former by a low. An increase in food availability may lead to both outcomes, dependent on the incidence of deaths of eggs.