Prey handling by a generalist predator, the golden eagle (Aquila chrysaetos)

Although the golden eagle (Aquila chrysaetos) is a well-studied raptor, there is a lack of studies on its prey handling-behaviour, which is important for understanding its prey selection. I extracted data on four individuals of the golden eagle from video footage, where the golden eagles were fed 32 avian prey, 29 mammalian prey, and 4 pieces of pure meat to see whether the golden eagle handled pure meat different than natural prey. I analysed the plucking and feeding behaviour for each feeding trial. Both number of plucks and plucking time for avian prey increased with prey body mass. It was more efficient for the golden eagle to feed on and handle a mammalian prey than to feed on and handle a similar-sized avian prey. Piece size decreased with increasing prey body mass for both prey types, while a piece from a mammalian prey was twice as large as a piece from a similar-sized avian prey. Further, the amount of non-ingested remains increased with increasing prey body mass, and there were more remains from an avian prey than from a similar-sized mammalian prey. Handling efficiency was higher for pure meat than for avian prey but did not differ from mammalian prey, while feeding efficiency were the same for pure meat and for both prey types. The golden eagles were most likely to start feeding from the breast of avian prey, and from the head of small mammalian prey. Further, the golden eagle were more likely to swallow mammalian prey whole than avian prey, due to more amounts of noningested parts in avian prey. Smaller prey were more profitable than larger prey, and mammalian prey were more profitable than avian prey. Thus, based on the cost of prey handling, golden eagles should select smaller prey, and mammals rather than avian when self-feeding.