Reproductive decisions of boreal three-toed woodpeckers (Picoides tridactylus) in a warming world: from local responses to global population dynamics

Abstract

Here, I examine whether both nestling prey abundance and profitability affect the timing of reproduction and hence the number of fledglings of three-toed woodpeck-ers, Picoides tridactylus. Individuals living in eastern Finland reproduced earlier and reared larger broods in habitat patches where the bark-beetle community developed earlier and/or faster and where the wood-boring beetles, whose larvae account for the bulk of the nestlings’ diet, were more abundant. As expected, mean breeding success increased with spring temperature, if laying date was related to prey phenology, which is temperature-dependent. However, using a larger data set with more years, adults seemed to face increasing difficulties in optimising their reproductive effort above certain spring temperature threshold, with a dramatic reduction in natal dispersal and winter population size over Finland following the warmest springs. I suggest climate-mediated phenological disjunction between the predator and its prey to be a likely cause of further decline in the insect specialist three-toed woodpecker.