Demographic patterns in winter carcass use by Golden Eagle and White-tailed Eagle in Finnmark, Norway

Abstract

The carcass use of juveniles, subadults and adults of the two eagle species in Norway, the White-tailed Eagle (Haliaeetus albicilla) and the Golden Eagle (Aquila chrysaetos) was studied in Finnmark, the northernmost county of Norway for two winters, in 2009 and 2010. Artificial carrion was laid out as bait on four peninsulas, along with automatic digital cameras which took picture on 5-15 minutes interval. The pattern of carcass use was evaluated in relation to distance from coast and forest, altitude, peninsula, year and day of the year. Furthermore, I investigated whether there were differences in the time spent scavenging each day. Juvenile eagles of both species and subadult White-tailed Eagles were rare on the carcasses, while subadult Golden Eagles and adults of both species occurred at similar, but overall, rather low frequencies. In general, occupancy on carcass decreases with distance from coast for both species, most clearly so for adult White-tailed Eagles. Subadult Golden Eagles were fairly evenly distributed across the peninsulas. Adult Golden Eagles were more common on the Sværholt and Varanger peninsulas, while adult White-tailed eagles were most common on the Nordkinn and Sværholt peninsulas. I detected no differences between the age groups in time period spent scavenging per day. The intensity of use of the carrion was too low in both eagle species for interference competition for such food resources to be a likely determinant of the spatial and temporal distribution of eagles during the winters in Finnmark.