Survival prospects of single-brooded and double-brooded Rock Pipits Anthus petrosus

Abstract

In a small, colour-ringed population of migratory Rock Pipits in the Gulf of Finland, no apparent impairment in survival prospects emerged among yearlings that bred twice in their debut breeding (double-brooded) compared with those that only bred once (single-brooded). Of the several variables measured, only timing of breeding differed between single- and double-brooded individuals: single-brooded birds bred about two weeks later than double-brooded birds. However, the occurrence of doublebroodedness increased with increasing age. The frequency of double-broodedness was lowest in years when winters were harsh in NW Europe. Hence, depending on the timing of spring, many Rock Pipits may start their breeding career prudently as singlebrooded but turn double-brooded in subsequent years. Reproducing once or twice in a season seems to be a joint product of age-dependent breeding schedule and concurrent environmental constraints.