Survie en milieu insulaire : quelle stratégie? Le cas des mésanges en Corse

Abstract

The breeding biology and demography of Blue tit (Parus caeruleus) and Coal tit (Parus ater) populations of southern France and Corsica were compared from 1976 to 1980. The following differences between the mainland and the island populations were found : 1. — The onset of the breeding season is delayed in Corsica, egg-laying beginning three to four weeks later than on the mainland. 2. — The clutch-size is smaller on the island, the clutch averaging three more eggs on the mainland. 3. — The mortality of the nestlings is also much higher in Corsica than in southern France, due to heavy parasitism by Trypocalliphora sp. and food shortage which cause heavy mortality. 4. — However, the survival rate of adult tits is higher in Corsica than on the mainland. 5. — Contrary to what is the rule in southern France, Corsican tits do not apparently breed at the time of maximum food abundance. The demographic strategies of the Corsican populations of Blue and Coal tits are apparently K-selected.