Justification of Red List Category
The population was estimated in 2016 to be 1,000-2,250 individuals (R. Thorstrom in litt. 2016), which was roughly equivalent to 670-1,500 mature individuals. It is now estimated that there are fewer than 1,000 mature individuals (L. Rene de Roland in litt. 2020). The global population is therefore placed in the band of 500-999 mature individuals. The subpopulation structure is not known, but given the species's wide range and fragmented habitat, it is assumed that there are multiple subpopulations and that fewer than 89% of mature individuals are found in a single subpopulation.
The population is inferred to be in decline owing to ongoing deforestation. An analysis of remote-sensed data on deforestation between 2000 and 2012 (Tracewski et al. 2016) estimated a rate of forest loss of 10% over three generations for this species.
Accipiter henstii is a forest raptor sparsely distributed throughout most of Madagascar but absent from the south-west (Langrand 1990). It is rare throughout its range (Langrand 1990, Morris and Hawkins 1998), but appears to be present in almost all adequately large forest blocks that have been surveyed (ZICOMA 1999).
It occurs in primary forest, both dry deciduous and humid evergreen, and in some secondary woodlands and large Eucalyptus plantations, not always near primary forest, up to 1,800 m (del Hoyo et al. 1994). It has a large home range size and lives at low densities, making it vulnerable to population declines, and may be declining more rapidly than currently thought (R. Thorstrom in litt. 2016). It hunts below the canopy for birds and small mammals, probably including some lemurs (Langrand 1990, Morris and Hawkins 1998). Egg-laying takes place in October-November, and the nest is large and constructed from sticks in the main fork of large trees, including those in Eucalyptus plantations (del Hoyo et al. 1994).
The species is considered vulnerable to deforestation (del Hoyo et al. 1994), and doesn't tolerate human disturbance (R. Thorstrom in litt. 2016). Forests in Madagascar are being destroyed as a result of slash-and-burn pasture and agriculture (Vieilledent et al., 2018), mainly for rice in the eastern regions, and maize in the drier west (Desbureaux and Damania 2018).
Conservation Actions Underway
CITES Appendix II.
A large forest accipiter. Even dark grey-brown above, with slight pale supercilium and pale, heavily-barred underparts, long yellow legs and long tail. Young birds are paler brown above, often with paler feather-bases showing, and are streaked brownish underneath. Similar spp. Very similar to Madagascar Serpent Eagle Eutriorchis astur, though the adult lacks that species' overall brownish coloration and dark bars in tertials, mantle and crown-feathers. Young birds are easily distinguished by having streaks, not bars, on the underparts. Flight is generally more direct and rapid than Madagascar Serpent Eagle. Almost identical in plumage to Madagascar Sparrowhawk Accipiter madagascariensis, but much larger; differs in having throat barred and streaked, forming a chequered pattern, and in usually having bars on the undertail-coverts. Hints Often seen flying over the forest canopy calling, a loud, rapid, rather cracked "ang-ang-ang-ang-ang-ang...". Otherwise, sometimes seen briefly while chasing birds in the sub-canopy or in clearings.
Text account compilers
Evans, M., Hawkins, F., O'Brien, A., Robertson, P., Réné De Roland, L.A., Starkey, M., Symes, A., Taylor, J., Thorstrom, R. & Westrip, J.R.S.
BirdLife International (2021) Species factsheet: Accipiter henstii. Downloaded from http://www.birdlife.org on 09/05/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 09/05/2021.