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

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