Telomere length, individual quality and fitness in female European starlings (Sturnus vulgaris) during breeding

Telomeres, short guanine-rich repeats that cap linear chromosomes, are involved in cell senescence and organismal ageing. Our present understanding of telomere function oscillates between a marker of individual quality, which should be positively correlated with reproduction, to a marker of costs of reproduction (e.g. due to DNA damage). To test these ‘quality’ and ‘cost’ hypotheses, we tested the output of very simple predictions in a free-living population of European starlings Sturnus vulgaris where reproductive success of adult females was followed over 2 breeding seasons (with 2 broods per breeding). If telomere length indicate individual quality, low quality females (LQ, no fledgling) should have lower telomere lengths than high quality females (which produced fledglings in 1st and 2nd broods). Additionally, physiological determinants of adult individual quality (established in a previous study) and provisioning rate should be positively associated with adult telomere lengths. Finally, telomere length should predict future reproductive success. Adult telomere length was lower in LQ females but only during the chick-rearing period. Females producing larger clutches at fledging in the 1st brood of the 1st year also had longer telomeres. Provisioning rate was positively related to telomere length, as were plasma markers of oxidative damage, non-esterified fatty acids and triglycerides. Despite these associations, we found weak support for telomeres as indicators of individual quality. Telomere length failed in predicting future reproduction success and there was a lack of consistency in within-individual telomere length over the breeding season. In starlings, we suggest that telomere length may indicate current breeding capacities and energy status of female adults, rather than future fecundity/survival.