Effects of spring body condition and age on reproduction in mallards (Anas platyrhynchos) / James H. Devries, Rodney W. Brook, David W. Howerter, and Michael G. Anderson.

Includes bibliographical references (pages 625-627).

We explored predictive models relating body condition and age to nesting propensity, timing of nest initiation, clutch
size of first nests, aggregated nest survival, hatching success, and timing of hatch in Mallards (Anas platyrhynchos). Nesting propensity had a positive linear relationship with body condition, and second-year (SY) females had a lower probability of nesting than after-
second-year (ASY) females (84% and 94%, respectively, at average body condition). Females in better body condition initiated nesting
~15 days earlier than those in poor condition, and SY females nested ~4 days later than ASY females at average body condition. Clutch
size of first nests exhibited a curvilinear decline with body condition, such that large clutches were characteristic of females in the best
condition that nested early. Nest survival and hatching probability were unaffected by body condition. Younger females had somewhat
lower nest survival (11%) than older females (14%), which, in combination with renesting effort, resulted in an age difference in hatching
probability (22% and 33%, respectively). Females in better condition hatched nests ~15 days earlier than those in poor condition, and
SY females hatched nests ~4 days later, on average, than ASY females. Our results indicate that factors influencing the body condition
of female Mallards arriving on breeding areas could influence subsequent reproductive investment and success. Condition effects are
primarily through the mechanisms of nesting propensity, clutch size, and timing of nest initiation and hatch. Additionally, we provide
evidence that Mallards in their first breeding season have lower reproductive potential than older females.