Nest predation in Blackbirds (Turdus merula) and the influence of nest characteristics

Abstract

Various studies have shown that predation rates depend on several factors, such as nest site and nest characteristics, nest defense and clutch size. However, the relative contribution of each factor in determining the observed patterns of nest predation remains an important question. We studied nest predation in a population of Blackbirds (Turdus merula) in an urban park located in Dijon (Eastern France) over two consecutive years. We used both natural and artificial nests (filled with dummy eggs). Overall, predation rate did not differ between natural (50%) and artificial nests (53%). Few species of predators were identified in the study site, and the red squirrel was the main predator (88% of the predation cases). Blackbirds used a large number of plant species as nest sites, but predation was not associated with this characteristic. A significant effect of nest characteristics (nest height, nest external diameter) on nest predation was detected for artificial nests but not for natural ones. These two factors may influence nest visibility, and may be important characteristics of nest exposure. Our results are consistent with those of previous studies and underline the importance of nest charcteristics on nest predation rate.