Current view: Data table and detailed info
Taxonomic source(s)
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
Gjershaug, J.O.; Kvalfy, K.; Rfv, N.; Prawiradilaga, D.M.; Suparman, U.; Rahman, Z. 2004. The taxonomic status of Flores Hawk Eagle Spizaetus floris. Forktail 20: 55-62.
IUCN Red List criteria met and history
Red List criteria met
Red List history
| Migratory status |
not a migrant |
Forest dependency |
high |
| Land-mass type |
|
Average mass |
- |
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.
Country/territory distribution
Important Bird and Biodiversity Areas (IBA)
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.
