EGG-PRODUCTION CONSTRAINTS AND THE EVOLUTION OF AVIAN CLUTCH SIZE

The aim of this study was to examine whether the capacity of female birds to produce high quality eggs could act as a constraint on the evolution of clutch size. By removal of the first laid egg; lesser black-backed gulls were experimentally induced to lay an additional egg. Their breeding success was then compared with a control group rearing the same clutch and brood size, The survival of chicks from the additional egg was only about a quarter of that of chicks from last laid eggs in the control group; it was found that this was largely an effect of reduced hatchling mass. The limited egg production capacity of females demonstrated by this experiment may in part explain discrepancies between predicted optimal and observed modal clutch sizes in birds.