ISLAND BIOGEOGRAPHY AND THE REPRODUCTIVE ECOLOGY OF GREAT TITS PARUS-MAJOR

Island biogeography theory has contributed greatly to both theoretical and applied studies of conservation biology (e.g., design of nature r eserves, minimum viable population sizes, extinction risk) and communi ty composition. However, little theoretical and empirical work has add ressed how island isolation and size affect reproductive ecology. We i nvestigated the reproductive ecology of great tits (Parus major) on on e offshore and one nearshore island, as well as on the Danish mainland . Tits breeding on the offshore island bred later, laid smaller clutch es, and laid larger eggs than those on the nearshore island and mainla nd. In addition, the level of ectoparasite infestation in nests was hi ghest on the offshore island, intermediate on the nearshore island, an d lowest on the mainland. These insular effects may occur due to lower food abundance on islands, to density-dependent effects, or to effect s related to low genetic diversity within island populations. Whatever the cause, the results emphasize that future studies of forest fragme ntation/population isolation should consider not only gross measures o f reproductive success, but also fine-scale measures such as clutch si ze, timing of breeding, and parasite prevalence.