Comparative reproductive biology of Middle Spotted Woodpeckers Dendrocopos medius and Great Spotted Woodpeckers D. major in a riverine forest

Abstract

Capsule Nest success rate and survival probabilities of individuals are the same but clutch size and fledgling number are higher in the smaller species. Aims To examine the relevant reproductive features of the two co-occurring congeneric woodpecker species, to analyse the effect of timing of breeding, clutch size and weather conditions on survival time of nestlings, and to discuss life-history traits in relation to potential food limitation and mortality. Results The start of the breeding season in both species was highly synchronized and did not vary among species and years. Middle Spotted Woodpeckers laid larger clutches (6.5 eggs) than Great Spotted Woodpeckers (5.4 eggs). Daily survival rates and the proportion of nestlings that were surveyed to the end of the nesting period, as well as nesting success (83% and 88%, respectively) did not vary between species. Middle Spotted Woodpeckers reared more fledglings in successful nests (4.5 fledglings) compared to Great Spotted Woodpeckers (4.0 fledglings). In both species the survival time of nestlings was negatively correlated with the timing of laying and the amount of rainfall during the incubation and nestling phase. Moreover, among Great Spotted Woodpeckers there was positive correlation between the survival time and the clutch size. Conclusion The highly synchronized start of the breeding season is probably conditioned by food availability. The difference between annual fecundity was a likely result of the higher winter mortality of Middle Spotted Woodpeckers. The survival time of nestlings was determined to a large degree by the timing of breeding and weather conditions. The west–east climate gradient is a plausible factor for the explanation of the longitudinal differences regarding the annual fecundity of European Middle Spotted Woodpecker populations.