With a little help from my kin: barn swallow nestlings modulate solicitation of parental care according to nestmates’ need

In altricial species, offspring competing for access to limiting parental resources (e.g. food) are selected to achieve an optimal balance between the costs of scrambling for food, the benefits of being fed and the indirect costs of subtracting food to relatives. Since the marginal benefits of acquiring additional food decrease with decreasing levels of need, satiated offspring should be prone to favour access to food by their needy kin, thus enhancing their own indirect fitness, while concomitantly reducing costs of harsh competition with hungry broodmates. We tested this prediction in feeding trials of barn swallow (Hirundo rustica) nestlings by comparing begging behaviour and food intake of two similar-sized nestmates, one of which was food-deprived (FD). Non-food-deprived (NFD) offspring modulated begging intensity depending on their nestmate’s need: when competing with FD nestmates, NFD nestlings reduced both the intensity and frequency of begging displays compared to themselves in...

在晚成雏物种（altricial species）中，为争夺有限的亲代资源（如食物）而竞争的子代，会通过自然选择在争抢食物的代价、获取进食的收益，以及抢夺亲属食物所产生的间接代价三者间达成最优平衡。由于获取额外食物的边际收益会随自身需求水平的降低而下降，饱腹子代更倾向于将食物获取机会让给有需求的亲属，以此提升自身的间接适合度（indirect fitness），同时还能降低与饥饿同窝幼鸟展开激烈竞争的成本。本研究以家燕（Hirundo rustica）雏鸟为对象开展摄食实验，通过对比两只体型相近的同窝幼鸟的乞食行为（begging behaviour）与食物摄入量（food intake）验证了上述预测，其中一只幼鸟为食物剥夺组（FD）。非食物剥夺组（NFD）雏鸟的乞食强度会根据同窝同伴的需求状态进行调节：当与食物剥夺的同窝幼鸟竞争时，非食物剥夺雏鸟的乞食展示强度与频率均会相较于自身在……情况下的表现有所降低。