The effects of environmental and individual quality on reproductive performance:A case study on blue tits

Birds have specific energetic requirements which likely depend on the habitat type they inhabit and on specific individual traits. Here, I investigated the effects of environmental quality (habitat quality and ambient temperature) and individual quality (age and/or lifespan) on features of reproductive performance in blue tits (Cyanistes caeruleus). Based on environmental factors, I showed that a higher proportion of deciduous trees surrounding the nest-sites, especially the density of English oak trees (Quercus robur), were good predictors of habitat quality and reproductive performance. I also demonstrated that the logging of coniferous trees has negative effects on blue tit reproduction. Environment had an effect on incubation. Controlling for ambient temperature, females took shorter recesses in high-quality habitats. Furthermore, the frequency of male incubation feeding of the female was lower in these habitats and when ambient temperature was higher.Based on individual features, female reproduction improved with female age and longer-lived females had an earlier age-specific laying date. There was no relationship between the female’s age-specific reproduction and the age or lifespan of the partner. As such it can be concluded that laying date and clutch size are female-determined traits.Older females maintained higher incubation temperatures and males increased the frequency of incubation feeding when their partners were younger and when females had later clutches. Male incubation feeding enabled the female to spend more time incubating. To conclude, the effects of environmental and individual quality interact and separating their effects on reproduction can prove extremely difficult and need longitudinal and experimental studies