Justification of Red List Category
This species is classified as Near Threatened because it has a small population which is undergoing a suspected decline owing to habitat loss.
The global population of Gurney's Eagles was suspected to be between 1,000 and 10,000 individuals (Ferguson-Lees and Christie 2001, 2005) however, there are an estimated 800-900 pairs of Gurney's Eagles in the North Moluccas alone (Røv and Gjershaug 2000) so the higher end of the global estimate may be more realistic (S. Debus in litt. 2016). The number of mature individuals is therefore placed in the band 2,500-9,999. The species is estimated to occur at a density of one pair per 33 km2 of land area in the North Moluccas (Røv and Gjershaug 2000).
The species is suspected to be in decline owing to habitat loss and degradation. For example, across mainland Papua New Guinea, 1.2% of forest was lost, and 2.4% of forest logged between 2002-2014 (Bryan and Shearman 2015). This translates to approximately 3.9% forest loss and 7.8% forest logging over the course of three generations (40 years) (Bird et al. 2020). Based on a long generation length and marginal forest loss and logging estimates therefore, the population is suspected to be undergoing a likely reduction of <10%.
Aquila gurneyi is a wide-ranging species of the Moluccas, Indonesia and New Guinea (Papua, formerly Irian Jaya, Indonesia and Papua New Guinea). There is an extralimital record from Biogu Island in Torres Strait, Australia (Beehler and Pratt 2016). There are no estimates of population sizes or trends but in Lakekamu Basin it is sparsely distributed in lowland alluvial forest (A. Mack in litt. 1999). Recent sightings include a subadult and juvenile at Danau Tolire on Ternate (Rheindt et al. 2014), individuals at Tofu Blewen (Irham 2012) and Seram (Reeve et al. 2014), single individuals and duos in Papua New Guinea (at Lake Kutubu Wildlife Management Area; Woxvold et al. 2019), records nearby Hegigio River gorge in the Southern Highlands Province, in the lower Purari River basin in the Gulf Province, in the lower Watut River (I. Woxvold in litt. 2020), and in the lower Waria River valleys in Morobe Province (Dawson et al. 2011). It is moreover regularly seen in the rugged hill forests of the Southern Highlands Province which remains largely unsuitable for logging (Woxvold et al. 2019; I. Woxvold in litt. 2020). Surveys on Obi island failed to find the species, though locals were familiar with the species (Mittermeier et al. 2013).
It appears to be widespread in a variety of forested habitats, including swamp forests (Coates 1985), although it appears to prefer primary forested habitats, spending the majority of its time foraging in such environments, as well as being observed in plantation, cultivated and logged forest alongside grasslands (S. Debus in litt. 2016). The species is frequently encountered below 1,000 m, although has been seen at 2,970 m (Beehler and Pratt 2016). It is thought to prey on arboreal mammals such as possums (Pratt and Beehler 2015), typically soaring low over the canopy whilst foraging, but occasionally perching on branches within the canopy (Røv and Gjershaug 2000). It is occasionally seen near flying fox (Pteropus sp.) colonies (I. Woxvol in litt. 2020). In New Guinea, this species slowly soars or circles above the forest canopy, often gliding on the wind above ridges (S. Debus in litt. 2016). It appears most prevalent in coastal locations where it uses onshore breezes, although it is often seen flying low over hilly country (Pratt and Beehler 2015).
It clearly occurs at low population densities and is likely to be declining slowly through habitat loss and degradation. For example, logging has been most extensive in lowland habitats overlapping the species's range in the Western Gulf and West Sapik (Sandaun) provinces (I. Woxvold in litt. 2020).
Conservation Actions Underway
CITES Appendix II.
Text account compilers
Everest, J., Fernando, E.
Benstead, P., Debus, S., Derhé, M., Dutson, G., Mack, A., Mahood, S., North, A., O'Brien, A. & Woxvold, I.
BirdLife International (2023) Species factsheet: Aquila gurneyi. Downloaded from http://www.birdlife.org on 24/03/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 24/03/2023.