Artificial floating islands for nesting Black-throated Divers Gavia arctica in Scotland: construction, use and effect on breeding success

Sixty-three artificial floating islands (rafts) were sited at Black-throate d Diver Gavia arctica territories in Scotland, the majority during 1992-95. Rafts were mainly 2.4 m x 3.6 m platforms made of polystyrene blocks on a wooden frame, covered with growing turf. Rafts were sited at lochs (lakes) where breeding success was low and/or nests had been flooded. Territory occ upancy, nest site and breeding success were monitored at territories with a nd without rafts during 1980-97. Rafts were used at least once at 44 territ ories, representing about one-quarter of the national population. Most raft s were used for the first time in the first or second year of provision. At territories where they where used, rafts improved chick productivity by a factor of 2.7 (95% confidence limits: 1.3-6.2). Raft provision probably imp roved the chick production of the Scottish Black-throated Diver population by 44% (7-130%).