There has recently been much interest in the long-term effects of early growth conditions. Telomeres, the repetitive DNA sequences that cap eukaryotic chromosomes, are potentially a useful tool for studying such effects. Telomeres shorten at each cell division and considerable evidence links the rate at which they do so with cellular and organismal senescence. Previous research has shown that telomere loss is greatest during early life, so conditions during this time could significantly affect telomere attrition, and in this way, possibly also senescence rates. However, relatively little is known about the pattern of telomere loss under natural conditions. We examined telomere dynamics during growth under natural conditions in the lesser black-backed gull Larus fuscus. Although telomere length significantly decreased with age during the chick period, there was a considerable amount of inter-individual variation in both absolute telomere length and the rate of telomere shortening. While no one factor explained a significant amount of this variation, the trends in the data suggested that circumstances during embryonic growth were linked to hatching telomere length. There was a trend for larger hatchlings to have shorter telomere lengths [effect size=−0.18±0.11 kb, 95% confidence interval (CI): −0.40, 0.05], suggesting that embryonic growth rate could have affected telomere attrition. Independent of this trend, males tended to have longer telomeres at hatching than females (effect size=0.77±0.40 kb, 95% CI: 1.55, −0.02). Egg volume and laying date had no relation to telomere length. There was a strong relationship between telomere length at hatching and at 10 days old (effect size=0.52±0.22, 95% CI: 0.94, 0.09), demonstrating that the variation in hatching telomere length caused by embryonic growth conditions remained consistent during the initial post-hatching period.