Sequential use of holes by birds breeding in a natural boreal forest in Mongolia

Capsule Wood Nuthatch Sitto europoea and Coal Tit Periparus ater had a high tendency to reuse nest-sites, and holes in living trees were more frequently reused than holes in dead trees. Aims Patterns of sequential nest-hole use are important in understanding the inter- and intraspecific relationships of hole-nesting birds. We studied the hole reuse at both guild and species level, and examined the characteristics of reused holes. Methods The fieldwork was carried out in a strictly protected area in Mongolia. Occupied nest-holes were searched for all hole-nesting species in two subsequent years. The characteristics of nest-holes and nest trees were recorded. Results Of 105 holes occupied in 2002, 40 (38%) were reused in the following year. The reuse rate for holes previously used by non-excavators was 48%, and subsequent occupation was almost exclusively by the same species. Reuse rates for previous woodpecker and Willow Tit Poecile montanus holes were 31% and 16%, respectively, and the subsequent users were more frequently a different species. Nuthatches and Coal Tits had the highest propensity to reuse holes. Holes located in living parts of trees were reused more often than those in dead wood. Conclusion The tendency to reuse holes could be influenced by the ability to excavate, the ability to compete for nest-sites, and the quality and abundance of preferred hole type of each bird species. The high reuse rate of certain holes would indicate good qualities and/or more limited availability of such holes. The more stable microclimate and greater protection from predation might account for the frequent reuse of holes in living wood.