Breeding performance, natal dispersal, and nest site fidelity of the three-toed woodpecker in the German Alps

Abstract

I studied the breeding biology of the three-toed woodpecker Picoides tridactylus in order to determine factors that influence annual and seasonal variations. Data from 37 pairs showed that 79% of nests produced at least one fledgling. The median laying date was not affected by elevation, and annual clutch and brood sizes did not differ significantly across the years. Seasonal trends supported the advantage of early breeding. More than 70% of clutches were laid within the span of 9 calendar days. Clutch and brood sizes declined with later laying dates and earlier breeders were more successful. Females paired with older males laid eggs earlier than those that were paired with younger males. Woodpeckers showed nest site fidelity across the years. Laying date relative to the rest of the local population, rather than the absolute laying date, should be regarded as an important determinant for breeding success in three-toed woodpeckers.