Nest-sites, breeding failure, and causes of non-breeding in a population of British marsh tits Poecile palustris

Capsule: Choice of nest-site appeared flexible and the rate of breeding failure was low, but some birds did not reach the nesting stage. Aims: To analyse nest-site selection and its effect on nest predation and establish the rate of breeding failure. Methods: We used vegetation sample plots to assess the nest-site resource and established the fate of birds in 153 territories and 134 nests over seven years. The fate of 30 nests from neighbouring woods was also determined. Results: Most nests were situated 0–4 m high in knotholes in live, medium-sized Common Ash trees. Overall, birds in 12.4% of occupied spring territories did not reach the nesting stage, primarily because of an absence of females, and 16.4% of nests in the same population were not successful. The nest failure rate was 18.4% across a wider population, which included neighbouring woods, primarily because of nest predation. Conclusion: Marsh Tits were flexible in their choice of nest-site with low rates of nest competition and predation. Nest failure is unlikely to be a significant factor in the decline of British Marsh Tits but failure to reach the nesting stage may be an additional pressure.