Rhinoplax Vigil Research Articles

Foraging characteristics of an assemblage of four Sumatran hornbill species

This study examines the diets of four hornbill species (Bushy-crested Hornbill Anorrhinus galeritus, Wreathed Hornbill Aceros undulatus, Rhinoceros Hornbill Buceros rhinoceros and Helmeted Hornbill Buceros vigil) common within our 9 km2 study area in the Bukit Barisan Selatan National Park, Sumatra, Indonesia. Line transects and opportunistic sampling were used over one year to collect feeding data, including the tree species and strata in which birds fed, diet items, fruit characteristics and tree crop size. Hornbills fed on 64 species. Figs, non-fig fruits and animals comprised 23.4% (n = 15 species) 51.6% (n = 33 species) and 25% (n = 16 species) of the diet, respectively. Although there was overlap among the diets of the four species, only B. rhinoceros and B. vigil had a statistically significant overlap, primarily due to high fig consumption by both species. B. vigil fed almost exclusively on figs (98.6% of the diet) and a small proportion of animals (1.4%) while 23.1% of the B. rhinoceros diet comprised non-fig fruits and animals (23.1%), with 76.9% figs. A. galeritus and A. undulatus had distinct diets with drupaceous, oily fruits comprising 66.7% and 64.4% of the diets, respectively. We found no significant relationship between the numbers of hornbills visiting fruiting trees and the characteristics of the fruit (weight, length and width). However, maximum crop sizes of diet species significantly influenced the number of feeding hornbills. Hornbill species also differed in the strata in which they fed. A. galeritus and B. rhinoceros were seen in the middle of the canopy 56% and 50.8% of the time, respectively while A. undulatus and B. vigil were observed more frequently in the upper canopy (50% and 74.3% of the time, respectively). The lower part of the canopy was used infrequently by all species. This study suggests that the four hornbill species in our study partition food resources by food type and/or feeding location.

Aerial jousting by Helmeted Hornbills Rhinoplax vigil: observations from Indonesia and Thailand

are unique amongthe Bucerotiformes in having solid ‘ivory’ casques that areused sometimes in aerial displays where individuals collidecasque-to-casque in mid-air (Kemp 1995). Knocking andabrasion during these aerial combats may even help toshape the distinctive flat, front profile of the adult birds’casques (Cranbrook & Kemp 1995). The behaviour hasbeen reported only among males, although females havebills and casques of similar structure and proportions tomales (Sanft 1960, Kemp 1995). Interactions, which maylast for up to 2 h, have been attributed to agonistic behav-iour and territorial defence (Kemp 1995) and to intox-ication from consumption of fermented figs (Schneider1945). Published descriptions of aerial casque-butting byHelmeted Hornbills are rare, and most observations arerecounted tales of other observers or, in the case of Kemp(1995), dramatized stories to illustrate the diverse behav-iour of the hornbill family (Cranbrook & Kemp 1995). Inthis note, we describe six acts of aerial casque-butting,hereafter referred to as aerial jousting, by Helmeted Horn-bills. For all jousts, we recorded the time of day, whetherthe jousting took place in or near fruiting trees, and thenumber and sex of the ‘actors’. We also report on the timeand location of five additional jousting events that wereinvestigated only after we were made aware of the behav-iour by the distinctive clacking sounds of colliding casques.The majority of observations were made over a 2-monthperiod (September–October 1998), as part of a largerstudy on hornbill foraging ecology (Hadiprakarsa 2000)at the Way Canguk Research Site, Bukit Barisan SelatanNational Park (BBS: 6 ° 37 ′ S, 101 ° 39 ′ E), Sumatra, Indone-sia. Three additional records were made at Way Cangukin 2000 and 2001, and one was noted at the Budo-SungaiPadi National Park (BSP: 5 ° 39 ′ S, 104 ° 24 ′ E), Thailand, in2000. The Way Canguk Research Site covers approxi-mately 900 ha of disturbed and undisturbed lowlandrainforest habitat in the south-east portion of the 3568-km

A spectrographic analysis of the loud calls of Helmeted Hornbills Rhinoplax vigil

Helmeted Hornbills Rhinoplax vigil inhabit the tropical and montane forests of Borneo, Sumatra, Malaysia, and Peninsular Thailand. Although little is known of their social behaviour and ecology, it is believed that they are monogamous and strictly territorial. The males have been observed to produce loud calls audible up to 2–3 km at various times throughout the day, but no studies of these calls have been made previously. An audiospectrographic analysis of the loud calls produced by several wild Helmeted Hornbills was conducted. The sounds comprising the loud calls were relatively pure in tone with few harmonics, with most of the energy produced between 500–1500 Hz, suggesting that selection may have favoured the long‐range transmission of these sounds through the forest. These calls are organized into two distinguishable parts, and it is suggested that the first part may primarily serve as a means of attracting the attention of neighbouring non‐mate conspecifics, while the second part may serve as an advertisement of age, size, or physical condition.

Wetmore on the Growth of the Tail Feathers of the Giant Hornbill A Peculiarity in the Growth of the Tail Feathers of the Giant Hornbill (Rhinoplax vigil) Wetmore

Wetmore on the Growth of the Tail Feathers of the Giant Hornbill A Peculiarity in the Growth of the Tail Feathers of the Giant Hornbill (Rhinoplax vigil) Wetmore