These data consist of relative telomere length (RTL) measures from quantitative polymerase chain reaction, of Seychelles warbler birds on Cousin Island, Seychelles. The data were collected by the Seychelles Warbler Project in 1995-2014. Data include bird identity, sex, age, birth period, qPCR plate identity, RTL, technician, territory, field period, mum ID, dad ID, mum age at conception, dad age at conception, dominant female ID in the natal territory, dominant male ID in the natal territory Full details about this dataset can be found at https://doi.org/10.5285/8a8240a2-e8ed-495d-ae93-c35200956764
