Reproductive output and telomere dynamics following calcium supplementation in wild Tree Swallows (Tachycineta bicolor)

This data was the result of an experiment investigating whether
biologically relevant differences in reproductive investment influence
fitness in a wild bird species. We employed calcium supplementation to
experimentally modify reproductive output in Tree Swallow mothers and
offspring and we used telomere dynamics during the breeding season as a
proxy for fitness. To confirm that calcium supplementation positively
impacts reproductive parameters at our study site, we initiated a 4-year
trial of calcium supplementation with our Tree Swallow study population.
In the following two breeding seasons, we used calcium supplementation to
experimentally alter reproductive output and measured telomere length in
mothers immediately before egg-laying and shortly before fledging to
determine the direct relationship between reproductive investment and
telomere shortening in this species. Our study includes one
hundred eighty-eight nests initiated and monitored over six breeding
seasons.