LARGER CLUTCH SIZE INCREASES FLEDGING SUCCESS AND OFFSPRING QUALITY IN A PRECOCIAL SPECIES

1, We tested the hypothesis that the ability of parents to raise viabl e offspring limits clutch size in the greater snow goose (Anser caerul escens 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 increase d in enlarged broods and decreased in reduced broods compared to contr ol. Consequently, enlarged broods fledged more offspring and the rever se was true for reduced broods. 4. Size and mass of goslings near fled ging was also higher in enlarged broods than in control, which suggest s that offspring quality was also enhanced by the manipulation. This i s contrary to the common trade-off between offspring numbers and quali ty. 5, Large families were dominant over smaller ones in feeding sites , which could explain the increased survival and growth of enlarged bl oods. 6, Our results suggest that the ability to raise young does not limit clutch size in this species and that parents could be more succe ssful(i.e. increase both the number and quality of their offspring) by laying more eggs. However, the time required to lay additional eggs r educes the viability of all offspring and may explain why females do n ot lay more eggs.