Justification of Red List Category
This species is listed as Endangered because it has a very small population which is declining owing largely to unsustainable harvesting of its eggs, disturbance of nesting sites and the degradation of wetland habitats in Madagascar. Declines are predicted to continue into the future.
Population data for Madagascar and the Seychelles, from a number of sources, suggests a population range of 2,300-2,750 individuals, roughly equivalent to 1,500-1,850 mature individuals.
The species's population is estimated to have declined by >20% over the last 16 years (two generations) based on comparison of current rarity (e.g. low numbers recorded on African Water bird Census) and historical accounts (e.g. Rand 1936), with most of this decline likely to have occurred in the last few decades (R. Safford in litt. 2006). The species's decline in Madagascar is shown by surveys in 2005 and 2006, in which 24 of the 26 sites revisited after surveys in the previous ten years showed drastic reductions (Andrianarimisa and Razafimanjato, 2011). However, the species's population increased at Bay de Baly between 2000 and 2004, and appeared stable at Mahavavy Delta between 2002 and 2005 (R. Rabarisoa in litt. 2007).
The specific status of Threskiornis bernieri as distinct from T. aethiopicus has been discussed for some time (Sibley and Monroe 1990, Lowe and Richards 1991, Dowsett and Forbes-Watson 1993) and is now accepted (BirdLife Taxonomic Working Group 2003). Two races are known: T .b. bernieri, found in the saline coastal zone and inland fresh water zone of western Madagascar (R. Rabarisoa in litt. 2007, Andrianarimisa and Razafimanjato 2011) (fewer than 2,500 [Wetlands International 2002, F. Hawkins in litt. 2003], maybe as low as 1,200 mature individuals [Delany and Scott 2006], but latest estimates put the Madagascan population size at c.2,000 mature individuals [Andrianarimisa and Razafimanjato 2011, Perschke 2006, Andrianarimisa 2006] and declining [Wetlands International 2002, F. Hawkins in litt. 2003, Andrianarimisa and Razafimanjato 2011]), and T. b. abbotti on Aldabra, Seychelles (300-750 individuals [Rocamora and Skerrett 2001]), giving a total population of 2,300-2,750 individuals. The species's decline in Madagascar is shown by surveys in 2005 and 2006, in which 24 of the 26 sites revisited after surveys in the previous 10 years showed drastic reductions (Andrianarimisa and Razafimanjato 2011). However, the species's population increased at Bay de Baly between 2000 and 2004, and appeared stable at Mahavavy Delta between 2002 and 2005 (R. Rabarisoa in litt. 2007).
Behaviour This species is sedentary, showing no evidence of either dispersal or migration (Hancock et al. 1992). Breeding is colonial and often occurs in mixed heron colonies (Morris and Hawkins 1998), with some mixed-nesting sites contained up to 200-250 nests of this species (Koenig 2012). Roosting also occurs colonially in groups of several dozen (Langrand 1990). It sometimes feeds alone but more often in pairs or small groups (Langrand 1990). Breeding has been observed at the start of the rainy season in the months of November and December (Langrand 1990). Habitat The species is believed to be ecologically more restricted than its African counterpart, being largely confined to lowland habitats (mean altitude of 91 occupied sites: 14.9m asl ± 3.81 SE, range 0 - 191 m asl [Andrianarimisa and Razafimanjato 2011]) in saline and brackish coastal zones, mainly mudflats, estuaries, mangroves and shallow brackish coastal lakes. During 2005 and 2006, 82.8% of birds surveyed and 69.2% of occupied sites surveyed or known from the literature were within 2 km of the coastline (Andrianarimisa and Razafimanjato 2011). There are also observations from inland rice fields and freshwater lakes within forested areas, such as the Manambolomaty complex (Tingay and Gilbert 1999, R. Rabarisoa in litt. 2007). It breeds near to its foraging grounds (Morris and Hawkins 1998) and roosts on islets or in trees in the same area (Langrand 1990). Diet It feeds on worms, small crustaceans, snails, insects, spiders and various organic materials (Andrianarimisa and Razafimanjato 2011). It will sometimes take small vertebrates including frogs, reptiles and young birds (Langrand 1990). Breeding site The clutch of two is laid in a small twig nest placed in a tree. It may also nest on the ground (Morris and Hawkins 1998).
Over 70% of the species's population in Madagascar resides outside protected areas (Andrianarimisa and Razafimanjato 2011). It is threatened in particular by the collection of eggs (F. Hawkins in litt. 2003, Andrianarimisa and Razafimanjato 2011), trapping of adults (Andrianarimisa and Razafimanjato 2011) and taking of nestlings for food (Perschke 2006, Andrianarimisa and Razafimanjato 2011), with drastic declines observed over widespread areas. It is fearless whilst nesting and roosting, making it an easy target for hunters (Andrianarimisa and Razafimanjato 2011). Existing legislation on hunting is weak and ineffective. The species is also threatened by habitat loss and degradation, with important habitats affected by pollution, sedimentation and the encroachment of alluvial sands. Increased sedimentation results from increases in soil erosion caused by slash and burn cultivation, and these effects are most prevalent in southern Madagascar where the species's population is low. In addition, mangroves are threatened with destruction for charcoal production (Perschke 2006). It is possible that the species is in competition for food with egret species, such as the Dimorphic Egret Egretta dimorpha (R. Rabarisoa in litt. 2007).
Conservation Actions Underway
Coastal sites are poorly protected in western Madagascar. New wetland conservation intiatives include this species as a conservation target (M. Rabenandrasana in litt. 2003). The Aldabra atoll is a Special Reserve of the Republic of Seychelles, providing the strongest level of wildlife protection where the only permitted human activities are nature conservation and restricted ecotourism (Rocamora and Skerrett 2001). In 2005, the Malagasy Association Voronosy was created to protect the species in Bombetoka Bay by changing the attitude of villagers towards the bird and its habitat (Perschke 2006). This has been carried out through posters, education in schools and notices warning against the taking of nestlings or felling of trees. Several projects to develop income-generating activities are underway. A boat will be used for fishing, eco-tourism trips and patrols to protect the species's breeding colonies. The protection measures resulted in an increase in the numbers of young birds in 2006 (Perschke 2006). A small number of captive breeding populations exist, including at Weltvogelpark Walsrode (www.rhinoresourcecenter.com).
65-89 cm. Unmistakeable large black and white ibis. Bare parts - bill, head, neck and legs - black. Primaries and secondaries tipped black, remainder white, although some birds have completely white primaries and secondaries (M. Rabenandrasana in litt. 2007). Similar spp. Easily separated from the all-dark Glossy Ibis Plegadis falcinellus and the forest-dwelling Madagascar Crested Ibis Lophotibis cristata. The pale iris differentiates this species from its African mainland congener.
Text account compilers
Allinson, T, Benstead, P., Butchart, S., Ekstrom, J., Khwaja, N., Symes, A., Taylor, J., Westrip, J.
Rabenandrasana, M., Rabarisoa, R., Skerrett, A., Tingay, R., Hawkins, F.
BirdLife International (2020) Species factsheet: Threskiornis bernieri. Downloaded from http://www.birdlife.org on 08/07/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 08/07/2020.