Age-Specific Reproduction in Three Species of European Ducks

Abstract

We tested the effects of female age on reproductive performance of Northern Shovelers (Anas clypeata), Tufted Ducks (Aythya fuligula), and Common Pochards (A. ferina) based on a long-term study (1958 to 1995) at Engure Marsh, Latvia. Yearling females initiated nests later than older (&2 years) females in each species, but female age explained little of the remaining variation in reproductive performance. Clutch size and brood size of all species declined seasonally. Age-specific increases in reproductive performance were most consistent between 1 and 2 years of age and were more apparent in the diving ducks than in Northern Shovelers. Clutch size, brood size, and duckling mass of yearling Tufted Ducks, and brood size and duckling mass of yearling Common Pochards, were smaller than those of older females. In Northern Shovelers, only duckling mass increased with age of the female. Nesting and hatching success did not vary by age for any species. Among 2-year-old females with and without previous breeding experience, experienced females nested five to six days earlier than inexperienced females in all species. Experienced, 2-year-old Tufted Ducks also had larger clutches and broods than inexperienced females. Effects of breeding experience generally lasted for only a single breeding season. Nesting date and duckling mass of yearling Northern Shovelers did not differ from that of inexperienced 2-year-olds. However, inexperienced 2-year-old Tufted Ducks and Common Pochards nested earlier and produced larger ducklings than did yearling females. Brood size of inexperienced, 2-year-old Common Pochards also was larger than that of yearlings. We found no evidence that age-specific increases in reproductive performance were related to differential survival of good breeders. Reproductive performance was constrained by past breeding experience in Northern Shovelers and by age and experience in Tufted Ducks and Common Pochards.