Larger clutch size increases fledging success and offspring quality in a precocial species

Abstract

1. We tested the hypothesis that the ability of parents to raise viable offspring limits clutch size in the greater snow goose (Anser caerulescens atlanticus L.), a precocial bird. 2. We manipulated clutch size by exchanging complete clutches between pairs of nests to increase or decrease the clutch size by zero (control), one, two or three eggs in 314 nests over 2 years. 3. Pre‐fledging survival of goslings increased in enlarged broods and decreased in reduced broods compared to control. Consequently, enlarged broods fledged more offspring and the reverse was true for reduced broods. 4. Size and mass of goslings near fledging was also higher in enlarged broods than in control, which suggests that offspring quality was also enhanced by the manipulation. This is contrary to the common trade‐off between offspring numbers and quality. 5. Large families were dominant over smaller ones in feeding sites, which could explain the increased survival and growth of enlarged broods. 6. Our results suggest that the ability to raise young does not limit clutch size in this species and that parents could be more successful (i.e. increase both the number and quality of their offspring) by laying more eggs. However, the time required to lay additional eggs reduces the viability of all offspring and may explain why females do not lay more eggs.