Data Zone
Justification of Red List category
This species has a small population size estimated at 320-1,500 mature individuals spread across multiple islands in the Lesser Sundaic archipelago (Indonesia). Despite the spread of islands, birds are thought to comprise a single subpopulation, with birds occasionally dispersing across islands. The population trend of the species is thought to be declining slowly in response to habitat loss and degradation, and persecution by local people. Accordingly it is listed as Endangered.
Population justification
No formal population size estimate has been made, although a territory size (based on distribution and spacing of three territories) of 40 km2 was suggested by Gjershaug et al. (2004). More recently, a study of movement patterns suggested a smaller home range of 8.4-23.1 km2 (O. Hidayat in litt. 2024). In the absence of other data, a combination of these evaluations is used here. There is additional uncertainty presented by this species' habitat requirements. Citizen science data (eBird 2023) are aligned with reports (Eaton et al. 2021, Syartinilia and Setiawan 2021) that this species is tolerant of some habitat degradation, as long as stands of tall trees remain for nesting. The following estimates (by island) are considered minimum bounds by tying population densities to strictly well-forested habitat, with recognition (see end of account) that it may occur (albeit at lower densities) in neighbouring habitats also. On Lombok, the species appears to be rarely encountered (eBird 2023) and there is little forest (c.1,300 km2) left at this species' elevational range (almost entirely around Mount Rinjani) and most of which is at elevations not optimal (per Gjershaug et al. 2004). Lombok is therefore unlikely to host more than 40 pairs, but perhaps more than the 10 estimated by Raharjaningtrah and Rahman (2004). On Sumbawa, the latter authors estimated 38 pairs, but this too appears moderately pessimistic given the island hosts at least 2,000 km2 of suitable habitat (= c. 50-100 pairs) and possibly considerably more if the species' upper elevational limit of c. 1,600 m is accepted. The area of forest on Rinca and Komodo is small and it is unlikely that combined these islands host more than 10 pairs. On Flores, Raharjaningtrah and Rahman (2004) suggested only 27 pairs but the species is frequently encountered, including in partially degraded landscapes (eBird 2023). Here, the population most likely exceeds 40 pairs, and there is suitable habitat to host as many as 150-250, although the latter figure assumes 100% occupancy. At least another 20-50 pairs are estimated on Alor (Collaerts et al. 2013), although the latter authors suggested the island could host up to 100 if distributed throughout the island. The species has not yet been confirmed from Solor, Adonara, Lembata or Pantar, but on all of these islands some (limited) suitable habitat remains that could host up to an additional 30-80 pairs. There are immense uncertainties in compiling these data presented by not knowing densities away from Flores, or densities in different habitat types. Nonetheless, previous attempts to estimate the population size (e.g. Gjershaug et al. 2004) likely underestimated the area of suitable habitat in its range. Collating the totals given here, the population is estimated to be at least 160 pairs (320 mature individuals) but if the species is found to occur throughout degraded habitats on the islands, the population could be several times larger. Such a possibility is presented by Syartinilia and Setiawan (2021) who, on Flores, found the species to occur frequently at elevations of 1,000-1,500 m, and to readily feed in degraded habitats. The population is therefore estimated at 320-1,500 mature individuals.
Trend justification
No empirical data are available, but deforestation and persecution are the most prominent threats to this species. Between 2000 and 2021, forest cover was lost at a rate equivalent to 7.5-10% over three generations (27 years), which will almost certainly have caused a population reduction in this species. However, although tied to forest for nesting, N. floris is regularly observed hunting over degraded habitat (Syartinilia and Setiawan 2021, Eaton et al. 2021, Worho et al. 2022, eBird 2023) and it is unclear to what extent this is still contributing to declines given that rates of forest loss between 2018 and 2022 were minimal (Global Forest Watch 2023, based on data from Hansen et al. [2013] and methods disclosed therein). Persecution is probably the most critical threat to this species, with some local communities viewing the species as a pest due to conflicts with poultry (Verbelen 2014). This is known to keep densities low (or even extirpate the species) in some villages (J. Eaton pers. comm. 2023) and in the absence of evidence this threat has ceased, it is precautionarily assumed that this is still causing ongoing (albeit slow) declines.
Endemic to Nusa Tengarra (Lesser Sundas), Indonesia, where it occurs on the main islands of Lombok, Sumbawa, Komodo, Flores and Alor (Collaerts et al. 2013, Eaton et al. 2021). It has also been recorded on several satellite islands.
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. The 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. A territory size of 40 km2 per pair has been estimated (Gjershaug et al. 2004). More recently, a study of movement patterns suggested a smaller home range of 8.4-23.1 km2 (O. Hidayat in litt. 2024). Evidence suggests that breeding takes place during the dry season. Display flight and copulation have been observed on Flores in June-July, and the breeding season is thought to occur at a similar time on Lombok too (Suana et al. 2016; see also Gjershaug et al. 2004).
This species is persecuted because of conflicts with poultry (Verbelen 2014). As are other hawk-eagles in Indonesia, N. floris may also occasionally be kept as pets (being caught usually as chicks). Both these end-uses, and the overall threat of poaching/trapping, needs greater research to determine extent and acuity. Habitat loss and degradation is also a key threat; forest cover lost at a rate equivalent to 7.5-10% over the past three generations (27 years), although more recent annual rates of forest cover loss have been slower.
Conservation Actions Underway
Listed in CITES Appendix II, although international trade is not considered a key threat to this species. Occurs in several protected areas across Nusa Tenggara, although the protection this offers from persecution is unclear. Community-based conservation and education schemes run by Burung Indonesia aim to reduce offtake and minimise incursions into suitable habitat.
Conservation Actions Proposed
Ensure the survival of the species by securing further protected areas within its range. Reduce persecution and exploitation levels through local education programmes. Conduct further research on the species' population size, trends and range. Verify records from additional islands. Study movements and determine population structure.
Text account compilers
Berryman, A.
Contributors
Butchart, S., Dutson, G., Eaton, J., Gjershaug, J., Collaerts, P., Prawiradilaga, D., Verbelen, F., Crosby, M., Lehmberg, T., Ashpole, J & Hidayat, O.
Recommended citation
BirdLife International (2024) Species factsheet: Flores Hawk-eagle Nisaetus floris. Downloaded from
https://datazone.birdlife.org/species/factsheet/flores-hawk-eagle-nisaetus-floris on 25/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 25/12/2024.