Which is More Costly? The Effects of Migration vs. Overwintering on Telomeres of American Kestrels (Falco sparverius)

Little is known about the costs and benefits of different migration strategies. Telomeres are sequences at the end of chromosomes that prevent DNA degradation. Telomere length, and their ability to protect DNA, decreases with age and stress. We studied the telomere lengths of migrant and non-migrant American Kestrels to compare the relative stress and energetic demands of migration versus residency as wintering strategies. We captured nesting American Kestrels and classified migration strategy with hydrogen isotope analysis of claw samples. DNA was extracted from blood samples and telomere lengths were estimated by quantitative PCR (qPCR) using primers that bind to the telomeric repeat. This qPCR signal was normalized to the PCR signal from a single copy gene. Understanding the trade-offs between the costs of migration and overwintering is important for understanding the evolutionary ecology of migration and predicting how Kestrels may alter their wintering strategies in response to climate change.