Nest survival of birds in an urban environment in New Zealand

Abstract

We compared nest survival of three urban bird species over two seasons in Dunedin City: silvereyes (Zosterops lateralis), a recent self-introduced native that is very abundant; blackbirds (Turdus merula), an abundant exotic species; and fantails (Rhipidura fuliginosa), a native species that occurs in relatively low numbers in some urban habitats. We also used artificial nests to compare nest predation rates between residential gardens and bush fragments isolated within a residential matrix. Silvereye nests had highest survival (daily survival probability = 0.98), with early nests and nests situated higher in trees having higher survival. Blackbird nest survival was lower (0.966); higher nests had better survival. Fantail nest survival varied significantly between years (0.908 in 2006-07 and 0.987 in 2007-08). Predation was a major cause of fantail nest failure, despite fantail nests being highest off the ground (mean = 4.2 m cf. 2.8 m for blackbirds and 2.2 m for silvereyes). Mortality of fantails during the week following fledging was high (41%). Low nest and juvenile survival may result in low abundance of fantails in Dunedin City. Predation of artificial nests was unaffected by nest placement (central or peripheral in the tree/shrub) and was the same in gardens as in bush fragments, with rats (Rattus rattus), possums (Trichosurus vulpecula) and possibly mice (Mus musculus) identified as nest predators.