Quantifying trade-offs between life history traits is complex. In particular, the extent of trade-offs between reproduction and somatic maintenance remains difficult to quantify in wild animals. Using the dynamic nature of telomeres may help to elucidate this process. Telomere length (TL) is generally associated with longevity, as it tends to shorten with age, and can thus serve as a biomarker associated with future survival. However, TL varies widely among individuals within a population, as it can be influenced by individual and environmental factors. An increased reproductive effort appears to accelerate telomere erosion, making TL a potential biomarker to describe the trade-off between reproduction and future survival. On the other hand, TL partially explains individual performance, with longer telomeres being associated with higher reproductive success. This study investigates the factors contributing to TL variation among female Tree swallows (Tachycineta bicolor) from a wild population in southern Québec, Canada. Specifically, it assesses the effects of individual (ex. age, reproductive traits) and environmental (ex. habitat quality, density) factors on TL variation within and between females over the course of a breeding season in this species. Our results improve our understanding of telomere dynamics in wildlife populations and their potential use as biomarkers of reproductive performance.