I investigated the influence of regional climate, local weather, and nest box features on the reproductive success of mountain bluebirds (Sialia currucoides)
and tree swallows (Tachycineta bicolor). I also evaluated the relative influence of local weather and parental care behaviour on mountain bluebird nestling growth
and mortality. My results demonstrate that local weather can strongly influence the breeding performance of mountain bluebirds, with improved reproductive
success during years of less rainfall. I conclude that this influence is likely exerted directly through acute nestling mortality rather than through nestling growth and prolonged nestling stress. As well, I show that regional climate plays an important role in tree swallow reproductive success, with improved tree swallow breeding performance during years of lower Southern Oscillation Index values (El Niño conditions). I suggest that the affect of regional climate on tree swallow reproductive success is likely due to influences that ENSO and regional climatic patterns may have on the aerial insect prey base of tree swallows in our study region near Kamloops, BC. For mountain bluebirds, I found the influence of weather on reproductive success is dependent on nest box features, including nest box entrance type. This study has implications for conservationists and managers of grassland passerines in British Columbia and beyond, especially in light of global climate change.
