THE BREEDING BIOLOGY OF THE REDSTART PHOENICURUS-PHOENICURUS IN A MARGINAL AREA OF FINLAND

The breeding biology of the Redstart was studied in its marginal breed ing area in northernmost Finland during the years 1982-1994. The mean clutch size was higher than in move southern populations. Losses durin g the egg and nestling stages were negligible: hatching success (hatch lings per egg) and fledging success (fledglings per hatchling) were 0. 91 and 0.89, respectively. Only heavy rainfall decreased nestling surv ival. Our results show that population size is stable and breeding suc cess is good in this marginal breeding area compared to other breeding grounds. The population size fluctuated in parallel with the vole cyc le as expected if small (mammal) predators switch to taking birds when vole numbers are low.