Clutch Size and Breeding Performance of Marsh Tits Parus palustris in Relation to Hole Size in a Primeval Forest

Abstract

I studied Marsh Tit, a secondary hole nesting bird in an area with superabundant holes (primeval forest in the Białowieża National Park, E Poland), expecting to find no relationship between hole size and, either clutch size, or breeding performance. Analysis of about 350 nest histories collected over 13 years revealed, as expected, no difference between breeding in medium-sized or large holes, but birds using small holes (lowest 25th percen- tile) laid smaller clutches, fledged marginally fewer young and lost more broods than the birds using the two larger size classes. This variation was not due to differences in timing of laying or the age of females across the hole classes. It is proposed that the use of small holes persisted because of relatively low fitness costs of making such a sub-optimal choice.