Abstract
The impact of nest-box characteristics (design, position, content) on decisions where to roost or nest have rarely been experimentally investigated. Older studies claimed that secondary cavity-exploiters, such as tits (Paridae), prefer smaller boxes for roosting and larger boxes for breeding. Surprisingly, these aspects of box preference have to our knowledge not been examined in choice experiments. We therefore allowed free-ranging birds to use, as roosting or nesting sites, three box designs attached together on the same support, covering the range of box sizes used to attract Great (Parus major) or Blue (Cyanistes caeruleus) Tits in long-term investigations. We observed that medium-sized and large boxes contained disproportionally more avian excrements before nesting than small boxes. The large boxes also contained disproportionally more body plumages prior to nesting and Great Tit nests. Nest-box size therefore influenced where the birds roosted and nested. Potential costs and benefits of exploitation of boxes differing in size are briefly discussed.