Hatching Order and Seasonal Timing of Development Predict Bill Morphology of Nestling and Adult Lincoln's Sparrows

[摘要] Abstract. Traits under strong directional or stabilizing selection can nonetheless vary considerably if the selective forces impinging on them vary in strength or direction. Although such variation is commonly manifested between unrelated individuals, some of the largest differences occur between siblings because of differences in their developmental experience. This is exemplified by the broods of altricial birds, in which asynchronous hatching produces a competitive hierarchy that influences an individual's developmental rate and fitness. Using Lincoln's Sparrow (Melospiza lincolnii), I examined whether the order of hatching or the seasonal timing of development (another factor that influences offspring fitness and estimated as the date of initiation of the clutch from which an individual hatched) predicted variation in bill shape, a trait often under strong natural and sexual selection. I measured individuals as nestlings and as adults for a metric of bill shape (height/width) that is associated with a...

[学科分类] 动物科学

[关键词] beak;developmental constraint;developmental plasticity;hatching asynchrony;laying date;sibling competition