Sulawesi Hornbill Rhabdotorrhinus exarhatus Scientific name definitions

45 cm; female 370 g. Small, black hornbill with green gloss on back; just two hornbills occur on Sulawesi, with Rhyticeros cassidix rather larger, a white tail, a taller casque and brightly coloured facial skin in all plumages (1 Kemp, A.C. (1995). Bird Families of the World. The Hornbills: Bucerotiformes. Oxford University Press, Oxford. Close ). Male nominate race with white facial and throat plumage, but in life stained yellow , possibly by preen oil; bill pale yellow , black at base of lower mandible, with low, ridged casque brown; bare skin around eye and on throat dusky pinkish; eye red, legs and feet black (1 Kemp, A.C. (1995). Bird Families of the World. The Hornbills: Bucerotiformes. Oxford University Press, Oxford. Close ). Female smaller (wing 215–231 mm versus 226–245 mm in male) (1 Kemp, A.C. (1995). Bird Families of the World. The Hornbills: Bucerotiformes. Oxford University Press, Oxford. Close ), all-black facial skin and throat ; yellow stripe below eye (1 Kemp, A.C. (1995). Bird Families of the World. The Hornbills: Bucerotiformes. Oxford University Press, Oxford. Close ); casque and bill blacker than in male (and casque also shorter, ending midway along bill, rather than just before tip) (1 Kemp, A.C. (1995). Bird Families of the World. The Hornbills: Bucerotiformes. Oxford University Press, Oxford. Close ), with cream ridges across lower mandible and paler creamy tip. Juvenile like adult male, but smaller bill dull yellow, casque undeveloped, and eye dark brown (1 Kemp, A.C. (1995). Bird Families of the World. The Hornbills: Bucerotiformes. Oxford University Press, Oxford. Close ); develops yellow facial colours from 80 days old, female acquires adult colours from c. 90–105 days. Race sanfordi differs mainly in having pale creamy yellow ridges across lower mandible , with redder-brown casque ; juvenile may possess creamy superciliary (1 Kemp, A.C. (1995). Bird Families of the World. The Hornbills: Bucerotiformes. Oxford University Press, Oxford. Close ).

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Editor's Note: Additional distribution information for this taxon can be found in the 'Subspecies' article above. In the future we will develop a range-wide distribution article.

Lowland and lower montane primary forest, occasionally tall secondary forest, usually below 650 m but sometimes up to 1100 m; family groups sometimes in more open habitats including recently burned areas and regenerating treefall gaps (3 O’Brien, T.G. (1997). Behavioural ecology of the North Sulawesi Tarictic Hornbill Penelopides exarhatus exarhatus during the breeding season. Ibis. 139(1): 97-101. Close ).

Apparently sedentary and territorial.

Diet mainly fruit (c. 85%), especially lipid-rich species (4 Walker, J. S. (2007). Dietary specialization and fruit availability among frugivorous birds on Sulawesi. Ibis 149(2):345–356. Close ), of at least 34 plant species and 13 families, especially Ficus spp. (Moraceae), Alstonia sumatrana (Apocynaceae), Chisocheton kingii (Meliaceae), Canarium hirsutum (Burseraceae), Polyalthia glauca (Annonaceae) and Cananga odorata (Annonaceae) (3 O’Brien, T.G. (1997). Behavioural ecology of the North Sulawesi Tarictic Hornbill Penelopides exarhatus exarhatus during the breeding season. Ibis. 139(1): 97-101. Close ); also some small animals, mainly invertebrates (26% or 7% of items at two nests) (3 O’Brien, T.G. (1997). Behavioural ecology of the North Sulawesi Tarictic Hornbill Penelopides exarhatus exarhatus during the breeding season. Ibis. 139(1): 97-101. Close ), with, in one recent study, fruit forming by far largest percentage of diet (89·4%), invertebrates constituting 9·8% and vertebrates 0·8%, while figs (Moraceae) comprised a mean c. 67% of monthly diet of the present species and Rhyticeros cassidix (4 Walker, J. S. (2007). Dietary specialization and fruit availability among frugivorous birds on Sulawesi. Ibis 149(2):345–356. Close ). Forages mostly through foliage below canopy, slowly and rather methodically (1 Kemp, A.C. (1995). Bird Families of the World. The Hornbills: Bucerotiformes. Oxford University Press, Oxford. Close ). Reported to chase R. cassidix. Foraging territory when breeding 72–139 ha.

Considered to be generally quite noisy: gives loud piercing “kerrekerre ... kerrekerre”, with the four syllables repeated at short intervals; a staccato “clack”, similar to call of Anorrhinus galeritus; and a chicken-like cackling has also been described (1 Kemp, A.C. (1995). Bird Families of the World. The Hornbills: Bucerotiformes. Oxford University Press, Oxford. Close ).

Season mainly Feb–May in N Sulawei (5 Cahill, A.J. (2003). Nest-site characteristics of the Red-knobbed Hornbill Aceros cassidix and Sulawesi Dwarf Hornbill Penelopides exarhatus. Ibis. 145: E97-E113. Close ), prior to Rhyticeros cassidix in same region, but also reported laying in Apr and Oct. Co-operative and territorial, in noisy groups of 2–10 birds (mean four), with adult helpers of both sexes, but non-breeding females that deliver food to nest usually rejected (3 O’Brien, T.G. (1997). Behavioural ecology of the North Sulawesi Tarictic Hornbill Penelopides exarhatus exarhatus during the breeding season. Ibis. 139(1): 97-101. Close ). Nest on trunk or branch (5 Cahill, A.J. (2003). Nest-site characteristics of the Red-knobbed Hornbill Aceros cassidix and Sulawesi Dwarf Hornbill Penelopides exarhatus. Ibis. 145: E97-E113. Close ) in natural cavity or old woodpecker hole in large forest tree (mainly deciduous, more occasionally evergreen), always live, on average halfway up in tall canopy tree with a large girth (5 Cahill, A.J. (2003). Nest-site characteristics of the Red-knobbed Hornbill Aceros cassidix and Sulawesi Dwarf Hornbill Penelopides exarhatus. Ibis. 145: E97-E113. Close ), including sites used by R. cassidix. Cavity of 12 nests measured 27·1–107 cm (mean 61·8 cm) × 11–35 cm (25·9 cm), and entrance 11–47 cm (21·7 cm) × 5.4–21 cm (13·8 cm) (5 Cahill, A.J. (2003). Nest-site characteristics of the Red-knobbed Hornbill Aceros cassidix and Sulawesi Dwarf Hornbill Penelopides exarhatus. Ibis. 145: E97-E113. Close ). Nesting density of 0·75–4·2 nests/km² (5 Cahill, A.J. (2003). Nest-site characteristics of the Red-knobbed Hornbill Aceros cassidix and Sulawesi Dwarf Hornbill Penelopides exarhatus. Ibis. 145: E97-E113. Close ). Usually two dirty white (1 Kemp, A.C. (1995). Bird Families of the World. The Hornbills: Bucerotiformes. Oxford University Press, Oxford. Close ) eggs (size 47·3 mm × 34·8 mm) (1 Kemp, A.C. (1995). Bird Families of the World. The Hornbills: Bucerotiformes. Oxford University Press, Oxford. Close ) or chicks reported in wild, and nesting cycle 70–90 days (3 O’Brien, T.G. (1997). Behavioural ecology of the North Sulawesi Tarictic Hornbill Penelopides exarhatus exarhatus during the breeding season. Ibis. 139(1): 97-101. Close ); in captivity, four eggs, first laid nine days after sealing in, rest at two-day intervals, with incubation 28–30 days (reported as 16–19 days in wild) (3 O’Brien, T.G. (1997). Behavioural ecology of the North Sulawesi Tarictic Hornbill Penelopides exarhatus exarhatus during the breeding season. Ibis. 139(1): 97-101. Close ) and fledging c. 50–60 days (55–70 in wild), with most food delivered in early morning and afternoon (3 O’Brien, T.G. (1997). Behavioural ecology of the North Sulawesi Tarictic Hornbill Penelopides exarhatus exarhatus during the breeding season. Ibis. 139(1): 97-101. Close ); female seals herself into nest, starts remex and rectrix moult before laying, emerges with chicks at end of nesting cycle; male delivers food to nest inmates by regurgitation.

VULNERABLE. CITES II. Locally common, although loss of lowland forest has fragmented its range, especially in S Sulawesi. Generally less susceptible to negative effects of anthropogenic habitat modification than R. cassidix, provided at least some large trees remain (6 Winarni, N.L. and Jones, M. (2012). Effect of anthropogenic disturbance on the abundance and habitat occupancy of two endemic hornbill species in Buton island, Sulawesi. Bird Conservation International. 22(2): 222-233. Close ). Groups occupy home range of 1·5–2 km², and occurs in Manembonembo Nature Reserve (7 Bororing, R. F., I. Hunowu, Y. Hunowu, E. Maneasa, J. Mole, M. H. Nusalawo, F. S. Talangamin, and M. F. Wangko (2000). Birds of the Manembonembo Nature Reserve, North Sulawesi, Indonesia. Kukila 11:58–72. Close ), Tangkoko-Dua Saudara Nature Reserve (1 Kemp, A.C. (1995). Bird Families of the World. The Hornbills: Bucerotiformes. Oxford University Press, Oxford. Close ), Gunung Ambang Nature Reserve (8 Riley, J., and J. Mole (2001). The birds of Gunung Ambang Nature Reserve, North Sulawesi, Indonesia. Forktail 17:57–66. Close ), Dumonga-Bone (now Bogani Nani Wartabone) National Park and in Lore Lindu National Park, as well as in Anoa, Lapago, Wahalaka and Wabalamba Forest Reserves on Buton I (6 Winarni, N.L. and Jones, M. (2012). Effect of anthropogenic disturbance on the abundance and habitat occupancy of two endemic hornbill species in Buton island, Sulawesi. Bird Conservation International. 22(2): 222-233. Close ). Still hunted for food, and for keeping as pets.