Justification of Red List Category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (extent of occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
The global population is estimated to number approximately 300,000 individuals which equates to 200,000 mature individuals (Partners in Flight Science Committee 2013). The European population is estimated at 9,300-12,300 pairs, which equates to 18,500-24,500 mature individuals (BirdLife International 2015). Europe forms approximately 16% of the global range, so a very preliminary estimate of the global population size is 116,00-153,000 mature individuals, although further validation of this estimate is needed. Precautionarily the population is placed in the band 100,000-200,000 mature individuals.
This species has had stable population trends over the last 40 years in North America (data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007). In Europe the population size is estimated to be increasing (BirdLife International 2015) however given that the European population constitutes a small proportion of the global population the overall trend is considered stable.
Behaviour This is the most widespread of the Aquila eagles, ranging across the Nearctic and Palearctic (70°N to 20°S), and fringing Indomalaya and the Afrotropics. It is uncommon to scarce across its range. In general, the species is sedentary, with juveniles dispersing as far as 1000km in their first few years. Birds occupying the mostly northerly regions (>65°N), such as Alaska, northern Canada, Fennoscandia and northern Russia, migrate south. In the Nearctic there are southwards movements to southern Alaska and southwest USA in September, via regular flyways, in particular through southwest Alberta. In the Palearctic, movements occur in a broad front to wintering areas in southeast Europe, the Russian steppes, Mongolia, northern China and Japan. Juveniles and immatures will go as far as North Africa (Ferguson- Lees and Christie, 2001). Habitat The species occupies a wide range of flat or mountainous, largely open habitats, often above the tree line, from sea level to 4000m. In the Himalayas it has been recorded as high as 6200m (Watson, 2010). Diet The species’ diet is very broad, taking mammals, birds, reptiles, fish, amphibians, insects and carrion variously, depending on the regional prey availability. Prey taken are usually 0.5-4.0 kg and the species can hunt in pairs or small groups (Ferguson- Lees and Christie, 2001). Breeding Site Nesting occurs on cliff ledges and where these are not available, in large trees or similar artificial structures. Nests are constructed from sticks and are added to in successive years, growing to 2m in diameter. The breeding season spans March – August throughout the majority of its range, and in southern areas begins as early as November; whilst in the most northerly regions it will start as late as April (Ferguson- Lees and Christie, 2001).
The species was heavily persecuted in the 19th Century, and although this threat has diminished significantly with populations now generally stable, the species is still deliberately poisoned, shot and trapped, and it is declining in Spain and North America (Katzner, Smith, et al., 2012). In the past the species was affected by the use of organochlorine pesticides although this is not a significant problem today. There are records of mortality as a result of electrocution when perching on power lines, but no data to suggest any substantial demographic impact. Wind energy developments are a source of direct mortality for the species, particularly in California where wandering sub-adults are mostly affected (Watson, 2010). Future developments in flyways may affect migrating adult eagles, and locally may cause effective habitat loss and lead to collisions (Katzner et al. 2012b). In addition, afforestation, long term changes in food supply, including reduced livestock carrion through changing management practices and climate change, may threaten the species in future (Watson, 2010). Within the Mediterranean region, declines in rabbit populations as a result of Viral Haemorrhagic Pneumonia may have a negative effect on productivity (Fernández 1993).
Text account compilers
Ekstrom, J., Butchart, S. & Ashpole, J
BirdLife International (2019) Species factsheet: Aquila chrysaetos. Downloaded from http://www.birdlife.org on 14/11/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 14/11/2019.