Abstract

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.