Although early reproduction within a breeding season often leads to higher reproductive success in seasonal environments, it is still not well understood how reproductive success can be influenced by climate both indirectly through the timing of breeding or by directly altering parental behaviour. In this thesis, I investigate the role of ambient temperature in reproductive success through its effects on the timing of reproduction and brooding in a population of gray jays, Perisoreus canadensis. In chapter 2, I test whether (i) female gray jays adjust laying date in response to temperature, (ii) individual or environmental characteristics constrain this plasticity, and (iii) laying date influences reproductive success. Females laid earlier in warmer years than in colder years; females partnered with older males laid earlier than females partnered with younger males at colder temperatures, but not at warmer temperatures. Early layers were more likely to rear at least one nestling and have a dominant juvenile survive the summer. These findings suggest that male experience could advance female laying date at cold temperatures and subsequently increase the probability of a positive nesting outcome. Though cold temperatures appear to limit timing of reproduction in gray jays, previous work in this system suggests that cold temperatures could better preserve perishable winter food stores. Thus, in chapter 3, I test whether temperatures during early offspring development interact with timing of reproduction to influence reproductive performance. Colder ambient temperatures during incubation were associated with larger brood sizes than warmer temperatures among late breeders, but temperature did not influence brood size among early layers, indicating that costs of late breeding may be amplified by temperatures that are unfavourable for food storage. This thesis contributes to our understanding of the environmental factors that determine reproductive performance, both through effects on timing of reproduction and after eggs are laid.