On the importance of having a good mother: maternal investment affects duckling mortality risk in wood ducks

Abstract

Most avian populations experience more variation in recruitment than adult survival, and this drives much of the change in population growth rates from year to year. In duck species, the probability of duckling survival is an important component of recruitment into the breeding population. We investigated how variation in maternal investment in offspring by nesting female wood duck Aix sponsa affected duckling mortality (1‐survival) to 60 days of age using capture‐mark‐recapture techniques. Our primary sample consisted of 3035 ducklings, from 545 nests, that were marked with uniquely coded webtags on the day of hatch over nine nesting seasons (2008–2016). We also included 4437 hatch‐year and after‐hatch‐year individuals to increase precision on parameter estimates because some ducklings were not recaptured until after fledging. Duckling mortality was greatest during the first week of life and approached zero by the second week after hatching. We observed a quadratic effect of hatch date on duckling mortality suggesting that successful females improve fitness by nesting early in the year, but not too early (15 days before mean hatch). Increased egg volume and duckling mass reduced the probability of ducking mortality. Our results suggest that risk of mortality for ducklings is influenced, at least in part, by maternal effects, which are manifested through energy allocation and behavior during the breeding season. As such, individual heterogeneity among breeding females affects duckling mortality risk and likely the recruitment process for wood ducks.