Aims: To ascertain whether cavity-nesting bird communities are limited by experimentally-manipulated hole availability at managed beech and pine forests in northern Spanish highlands and to study the responses of non-cavity-nesting birds.
Location: North of Navarre (Spain).
Methods: Bird censuses were taken at breeding and wintering periods in study plots during 2001, 2002 and 2003. Nest boxes were placed in half of the study plots, and plots with and without nest boxes were compared for variation in nesting guild abundance and richness.
Results: Results showed an increase in cavity-nesting bird abundance and species richness between two breeding periods and in abundance between two non-breeding periods in the plots where nest boxes were added in both types of forest. No difference in abundance or richness during breeding was observed for the non-cavity nesting birds in plots where there was an increase in the abundance of cavity-nesters. However, an increase in abundance of non-cavity nesters in non-breeding periods was observed in plots where nest boxes were added in pine forests.
Conclusion: Results suggest that cavity-nesting bird communities were limited by the availability of suitable natural holes in the two forest types studied and highlight the importance of cavities outside the breeding season as shelter or roosting places for both cavity and non-cavity nesting bird communities.