Effects of island isolation and feral mink removal on bird communities on small islands in the Baltic Sea

摘要: Summary 1 Predation has been suggested as a major cause affecting survival, reproductive success and behaviour in vertebrate prey populations. The breeding season is critical phase because the essential difference between selecting proper nest site may be question of failure. 2 Islands serve refuges for ground-nesting birds against natural mammalian predators. However, many bird species on islands are currently threatened by introduced predators they lack mechanisms to confront threats new predator. 3 We studied combined effects an generalist predator, American mink (Mustela vison Schreb.), island isolation size richness, abundance equitability small outer archipelago SW Finland, Baltic Sea. study comprised two removal areas (one during 1993–2001 other 1998–2001) comparable control (during 1994–2001 1998–2001), each covering 72–130 km2, which 1·07 1·27 km2 were land area. mean all was < 2 ha. 4 In areas, both richness highest most isolated islands, while did not have obvious these variables areas. Species was influenced or isolation. 5 The distribution maritime species, razorbill (Alca torda L.), changed dramatically: 1973–74, before invaded area, found commonly less than 1994, after invasion. 6 We suggest that presence their selection started breed visited frequently islands. Therefore, our results indicate increasing increase number numbers, slows down dispersal.