WINTER SURVIVAL AND BREEDING SUCCESS OF DOMINANT AND SUBORDINATE WILLOW TITS PARUS-MONTANUS

We studied the effect of winter rank on survival rate and reproductive success in Willow Tits Parus montanus, a resident passerine living in dominance-structured necks during the nonbreeding season, in 6 years, Winter survival was dependent on both the birds' age and rank, Adults survived better than first-year birds, and within first-year males, d ominants survived better than subordinates, In other sex and age class es, rank did not contribute to survival. Although first-year males wer e in excess among nonbreeders, no connection existed between breeding status and rank. Female rank did not explain the variation in the star t of laying, clutch size, number of fledglings or recruit production, We conclude that social status in Willow Tits affects individual fitne ss mainly through rank-dependent survival. Acquiring a high rank posit ion seems to be most important for first-year birds, especially first year males.