Interspecific Dominance and Risk-taking in Three Species of Corvid Scavenger.

Abstract

I studied the risk-taking behaviour of three species of corvid scavenger at carcasses during a severe winter. The dominance hierarchy was clear-cut, with ravens Corvus corax being most dominant, hooded crows Corvus corone intermediate, and magpies Pica pica least dominant. Dominant species generally excluded subordinates from access to the carcass. As predicted, the most subordinate species present was almost always the first to move to the carcass when it was unoccupied, either after first light or after a "panic" in the feeding flock caused by the real or apprehended presence of a predator in the vicinity. When relative abundance of each species was taken into account, this result was very highly significant both when magpies were the least dominant species present and when hooded crows were the least dominant species. This was despite apparent vulnerability to predation being highest in magpies and lowest in ravens. Alternative hypotheses to explain the data are considered. The evidence suggests that the least dominant (and so hungriest) species were willing to accept the cost (higher predation risk) involved in being the first individual to move to the carcass, in order to obtain the benefit of food from which they were normally excluded.