Flores Hawk-eagle (Nisaetus floris) is found in Indonesia, on the islands of Flores, Sumbawa and Lombok as well as on two satellite islands, Satonda near Sumbawa and Rinca near Flores (Gjershaug et al. 2004). The species has also occurred on Komodo, with an individual photographed on a mangrove islet less than 800 m offshore in 2011 (Coates and Bishop 1997, Collaerts et al. 2013). It has recently been discovered on Alor and is apparently present throughout the island (Collaerts et al. 2013). A record from Paloe (Verheijen 1961) has not been confirmed. Its population size has been estimated at fewer than 100 pairs, based on the extent of suitable habitat and a territory size estimate of c. 40 km2 (Gjershaug et al. 2004), although it is estimated that at least 20 additional pairs inhabit Alor (Collaerts et al. 2013). The lack of records obtained during fieldwork within its range suggest it occurs at low densities, supporting this population estimate. Population trends are not known, but it is assumed to be declining owing to on-going forest loss in the Lesser Sundas.
This species has an extremely small population that is undergoing a continuing and very rapid decline as a result of habitat clearance, and as a consequence it is listed as Critically Endangered.
On the basis of distances between three neighbouring territories, the species’s territory size was estimated at c. 40km2. Given that it is primarily dependent on forest, this implies that the total population size for the species is probably less than 100 pairs or 200 mature individuals. In addition at least 20 pairs have been estimated to occur on the island of Alor, representing another 40 mature individuals. It is estimated at 100-240 mature individuals, roughly equivalent to 150-360 individuals in total.
No empirical data are available, but deforestation and persecution are likely to be causing an on-going decline. Given the species’s longevity scaled over the past three generations it has almost certainly experienced a very rapid decline.
It is found in lowland and submontane forest up to 1,600 m, with the majority of observations being made in lowland rainforest. It has been sighted over cultivated areas, but always close to intact or semi-intact forest; these records may relate to dispersing, immature or floater individuals rather than breeding adults. These records of birds outside core habitat suggest that the species may be able to disperse across the relatively narrow straits between islands so mixing between island sub-populations is inferred. Evidence suggests that breeding takes place during the dry season. Display flight and copulation have been observed on Flores in June-July. A territory size of 40 km2 per pair has been estimated (Gjershaug et al. 2004).
Habitat degradation and destruction are the most important threats; records are infrequent and it has rarely been recorded during trips to several large forest tracts suggesting extreme low density and casting some doubt on the assertion that it may be able to survive in a partly cultivated landscape. Protected areas in its range are currently too small to ensure its long-term survival. Persecution, due to its habit of preying on chickens, is another threat. In April 2014 an individual was shot in central Alor and the reason given was because the birds take chickens (Verbelen 2014). Capture for the cagebird trade is also a threat.