Data Zone
Justification of Red List category
This species's known range is considerably larger than once thought, and the use of playback techniques has demonstrated that it is not as rare as previously thought. Nevertheless, the species has a very small population, which is suspected to be undergoing a continuing decline as a result of the increasing destruction and fragmentation of its habitat through deforestation. Its ecological niche is also projected to greatly decline due to climate change. For these reasons it is listed as Endangered.
Population justification
The population is estimated at 66-1,660 individuals (0.04-1 individuals/km2 x 1,660 km2), but is perhaps best placed in the band 250-999 mature individuals. This equates to 375-1,499 individuals in total, rounded here to 350-1,500 individuals. Hawkins (in litt. 2003) suggests the total population is certainly not less than 250 individuals, and L.-A. Rene de Roland in litt. (2012) suggests 250-650 individuals. Assuming a body mass of 800-1,200 g, data in Newton (1979) suggests a breeding density of c. 0.04-1 birds/km2, however the body mass has since been estimated to average 700 g for males and 800 g for females (L.-A. Rene de Roland in litt. 2012).
Trend justification
Hawkins in litt (2003) suggests that the population decrease cannot be more than 30% over the past ten years, but modelling the possible effects of climate change have shown that this species's ecological may decline by as much as 94% due to climate change over the 50 year period from 2000 to 2050 (Andriamasimanana and Cameron 2013). Assuming a linear decrease, this would equate to an ongoing c.72% decline in ecological niche over 3 generations, placed here in the range of 70-79% (ongoing c.48% over 2 generations; c.35% in next generation).
Eutriorchis astur is a rare inhabitant of the eastern rainforests of Madagascar from Zahamena in the south to Marojejy in the north, and in the central high plateau at Anjozorobe and Bemanevika (L.-A. Rene de Roland in litt. 2012). Apart from inconclusive reports of its presence in Marojejy Reserve in the 1960s and 1970s, and despite considerable search-effort within its habitat, it was not definitely recorded between 1930 and 1993 (Thorstrom et al. 1995, R. Thorstrom and L.-A. Rene de Roland in litt. 2007). Since the clarification of the species's territorial call in 1995, it has been discovered at several new sites. Amongst other localities, it is most commonly observed in Masoala National Park, where at least 16 individuals have been recorded from nine sites (Wilcove 1999) and nesting attempts have been recorded, and at Makira Forest (R. Thorstrom and L.-A. Rene de Roland in litt. 2007). The population is almost certainly greater than 250 individuals (F. Hawkins in litt. 2003).
An elusive and wary denizen of lowland and mid-altitude primary rainforest, it rarely, if ever, ventures beyond the forest edge (Langrand 1990, Morris and Hawkins 1998, Thorstrom and Watson 1997). It is known to feed on lizards (chameleons and geckos, which make up 83% of its diet) and frogs (Thorstrom and de Roland 2000). It flies between subcanopy perches, hunting for prey in the trees and on the ground (R. Thorstrom in litt. 2016). It is also known to glide over the canopy and use foot-thrusting to flush prey in epiphytes and under leaf litter on the ground (R. Thorstrom and L.-A. Rene de Roland in litt. 2007). Between 1997-2005 a total of five nests were located on the Masoala Peninsula, all of which were placed inside epiphytic ferns, however at Bemanevika New Protected Area nests observed in 2007-2012 were constructed from sticks and placed in a tree fork 20-23 m above ground, with a clutch size of two (Peregrine Fund 1997, L.-A. Rene de Roland in litt. 2012). In one studied nest at Masoala the clutch size was one, incubation 40+ days, nestling period 62 days, and the young dispersed at 15 weeks of age. The species exhibits low productivity, producing one offspring every one or two years (R. Thorstrom and L.-A. Rene de Roland in litt. 2007).
Its forest habitat is being reduced by extensive clearance for subsistence slash-and-burn agriculture and also commercial logging activities. Other threats include uncontrolled bush fires and poor mining practices. The species dependence on pristine lowland to mid-altitude forest makes it particularly susceptible to disturbance. Human persecution may also be a problem in some areas (Thorstrom and Watson 1997). Much of the eastern coastal plain has either already been cleared or is covered by highly degraded forest; remaining habitat is under pressure from the increasing human population (Du Puy and Moat 1996). If present trends continue, the remaining forest, especially at the lower altitudes preferred by this species, will disappear within decades (Du Puy and Moat 1996). It is possible that numbers Furcifer and Calumma chameleons, and Uroplatus geckos, key prey species, are being reduced by capture for the exotic pet trade, but this has not been confirmed (Eames 2010). Climate change could be a great threat because as a much as 94% of its ecological niche could be lost due to climate change over the 50 year period from 2000 to 2050 (Andriamasimanana and Cameron 2013).
Conservation Actions Underway
CITES Appendix II. The species has been found in several protected areas, including four National Parks, one Strict Reserve, two Special Reserves and one Classified Forest, as well as at 10 of the 30 Important Bird Areas in eastern Madagascar (ZICOMA 1999). It may occur in other protected areas further south. It is the subject of an ongoing research program in the Masoala Peninsula (Thorstrom and de Roland 2000).
66 cm. A medium-sized, secretive forest eagle. Rather dull, pale earth-brown above, with narrow, blackish barring in crown, nape, some ear-coverts, and wider black barring on the tertials, secondaries and primaries. Whitish below with wide irregular dark brown barring. Long tail, barred dark with paler margins to dark bars. Yellow eyes, stout bill but lacking tooth. Long, powerful, yellowish, heavily-scaled legs. Similar spp. Differs from Henst's Goshawk Accipiter henstii by paler earth-brown upperparts combined with horizontal breast-barring, inconspicuous dark bars in upperparts (especially tertials and on head), rather long tail, rather bulging head-shape with slight nape crest, and call. Voice Loud call, a far-carrying and measured wah...wah...wah...wah..., often followed by a lower rugh.
Text account compilers
Benstead, P., Ekstrom, J., Evans, M., Shutes, S., Starkey, M., Symes, A., Taylor, J. & Westrip, J.
Contributors
Hawkins, F., Réné De Roland, L. & Thorstrom, R.
Recommended citation
BirdLife International (2024) Species factsheet: Madagascar Serpent-eagle Eutriorchis astur. Downloaded from
https://datazone.birdlife.org/species/factsheet/madagascar-serpent-eagle-eutriorchis-astur on 23/12/2024.
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 23/12/2024.