Brood size is associated with apparent telomere lengthening in nestling barn swallows.

Early life for animals is often a time of rapid growth and development. In a resource-limited environment, life history theory predicts that there must be trade-offs between resource sinks in ways that optimize future survival and reproductive success. Telomeres have emerged as putative indicators of these early life trade-offs, but there are conflicting accounts as to how developmental traits and conditions impact telomere length and dynamics.