Food limitation explains most clutch size variation in the Nazca booby

摘要: Summary 1  Natural selection is expected to optimize clutch size, but intrapopulation variation maintained in many bird species. The Nazca booby provides a simple system which investigate size evolution because and brood are decoupled due obligate siblicide. indirect effect of on can therefore be eliminated. 2  In boobies, second eggs provide insurance against the failure first egg or early death hatchling, approximately half all females lay only one egg. We tested hypothesis that one-egg clutches result from food limitation by providing female boobies with supplemental food. 3  A higher proportion supplemented produced two-egg than did control females. Supplemented larger second-laid females, not first-laid eggs. Laying date laying interval were affected. 4  Comparisons volume between years indicated feeding experiment was conducted year poor natural supply. Thus sizes despite apparently normal levels. 5  This nearly completes our understanding booby, indicates costs egg-laying should considered carefully studies evolution.