Systematic ringing and subsequent resighting of 6 annual cohorts of young Guillemots indicated a high degree (42%) of philopatry to the natal group of 50–200 pairs. However, few young bred close to the sites where they were reared. There was no statistically significant sex difference. There seems little prospect that adjacent individuals, or even those breeding on a single ledge, are closely related.
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Harris et al. (1996) studied this question.
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