The Neophobia Hypothesis: nest decoration in birds may reduce predation by corvids.

Abstract

Many birds suffer heavily from nest predation, selecting several behaviours to avoid the risk. Corvids are among the most serious nest predators. However, they are also among the most neophobic of any birds. We suggest that nesting birds may take advantage of this fear by decorating the nest with anthropogenic materials that are novel to the predators (termed the Neophobia Hypothesis). They may also add large, conspicuous feathers that may indicate a site where a bird has recently been killed. In a study in the field, we found that territorial Eurasian magpies Pica pica waited for a longer period to remove eggs from artificial nests decorated with a shiny metal teaspoon, or with large, white feathers compared to adjacent artificial control nests with no decoration. On a landfill, where the birds had become more habituated to forage among anthropogenic material, common ravens Corvus corax also avoided nests decorated with a teaspoon or with feathers. The study supports the hypothesis that birds may suffer less nest predation by corvids if they decorate the nest with anthropogenic material or with large feathers.