Optimal maternal incubation strategies for altricial and precocial birds

Abstract

Parental management of early offspring development is a complex but essential contribution to reproductive success for oviparous species. Mothers faced with incubating eggs in a variable environment maximize reproductive success by adaptively adjusting offspring number in a clutch and incubation schedules to facilitate egg development while meeting their own energetic demands. However, the optimal resolution of these trade-offs varies with physiological and ecological factors and is thus hard to determine using empirical data from natural systems. To untangle the complex factors driving optimal maternal decisions, we developed an ecophysiological model that identifies optimal maternal strategies and their implications for offspring, comparing results for example altricial and precocial species. We showed how plastic maternal strategies can ameliorate effects of food scarcity, offspring mortality risk, variable levels of biparental care, and constraints on producing multiple clutches within a season. In the altricial case in particular, we identified important downstream fitness effects from decisions made in the incubation stage. Additionally, we showed that seasonal decreases in clutch size may result from cumulative fecundity costs for the altricial case and from a seasonal decline in female quality for precocial species. Many of the novel results in this study are testable in future empirical work.