THE AUK A QUARTERLY JOURNAL OF ORNITHOLOGY VOL. 99 APRIL 1982 NO. 2 MIMICRY OF FRIARBIRDS BY ORIOLES JAREDM. DIAMOND PhysiologyDepartment, University of CaliforniaMedical School, LosAngeles, California 90024 USA ABsTR•cT.--Friarbirdsand orioles show striking but parallel geographicvariation in plumageon islandsof the Australianregion, such that their populationson the sameisland are often closelysimilar in plumage.This parallelisminvolves mimicry of friarbirds by orioles,which are in turn mimicked by a smallerhoneyeater. The larger the friarbird com- pared to the oriole, the more perfectis the mimicry. Friarbirdsand oriolesare convergently similar in ecologyand morphologyand belong to a guild of birds that feed togetherin fruiting and flowering trees and that display much aggressiontoward each other. Within this guild, mimics are sparedfrom attack by larger models,which attackother smaller species.Other possiblysimilar casesexist among tropicalbirds. Received5 January1981, Accepted2 September1981. BIOLOGICALmimicry involves three roles: a are few well-established cases of visual mim- mimic, which resemblesanother speciesand icry in birds. thereby gains some advantage for itself; a Over a centuryago Wallace (1863, 1869: 305) model, which is imitated by the mimic; and a describedwhat he claimed to be an example signal receiver, which mistakes the mimic for of visual mimicry in birds, involving Old the model and thereby becomesthe victim of World orioles(genus Oriolus, family Oriolidae) the mimic'sdeception (Wickler 1968). Mimicry and friarbirds (genus Philemon,family Meli- may be visual, acoustic, chemical, or behav- phagidae) in the Australian region. Wallace's ioral. Familiar examplesof visual mimicry in- claim was disputed by Stresemann (1914a), clude nonpoisonous butterflies or snakes that however,and there has been no further study haveevolved to resemblepoisonous butterflies of this case. The present paper is based on or snakesin order to gain the advantageof study of specimensof all speciesof oriolesand being avoided by predators.Although many friarbirds and on field studiesof a coexisting bird speciesare famous as vocalmimics, there mimic oriole and friarbird (New Guinea), two Frontispiece.Adult plumages of friarbirdsand orioles.Large capital letters are island names, small letters are taxon names.Top row right: a typical oriole outside the range of friarbirds (Oriolusoriolus). Top row left: a typicalfriarbird outside the rangeof orioles(Philemon cockerelli). Top row center:on the LesserSunda Islandsan oriolelarger than the O. [bouroensis]superspecies and of typicalOriolus plumage, O. chinensis, coexistswith the westernmostmember of the P. [moluccensis]superspecies, P. buceroides.Rows 2-6: coex- isting friarbirdsof the P. [moluccensis]superspecies and oriolesof the O. [bouroensis]superspecies. The oriolemimics the sympatricfriarbird to varying degreescorrelated with the friarbird'ssize: Australiaand Timor have the smallestfriarbirds, and the two Australianoriole species and the maleoriole of Timor are not mimics,while the largestfriarbird (that of Ceram)is mimickedalmost perfectly. Pycnopygius sticto- cephalusis a smallerhoneyeater that mimics the New Guineaoriole. See Table 1 for details.Painted by H. L. Jonesfrom specimensin the AmericanMuseum of NaturalHistory. 187 The Auk 99: 187-196.April 1982 UMBO LES R SUNDAS EURASIA P. bucer, -ctus -• ß' O. chinensis P. cockereHi •,0. oriolus HALMAHE' CERA ' pious P. sue ßtus forsteni aeochromu• BUR ßens s O. b. bouroensis TENIMB' .decipiens WETA ' ? TIM R P lidiceps P.b bu , e8 •. v finschi J vi s P. novae. '•b'e Isis P NEW GUINEA :iu•, stictocephalus P. I10V * ctns AUSTRALIA 188 JAREDM. DIAMOND [Auk, Vol. 99 I I IOøN-- /' 140øE 15(Y'E I Philippines.'..'• Lesser $undas WeTM ___ IOOS - Fig.1. Mapillustrating overlap of oriolesand friarbirds. Dots: Oriolus but no Philemonpresent. Vertical hatching:Philemon but no Orioluspresent. Solid shading: both Philemon and Oriolus present; solid under- liningof islandname indicates mimic oriole, dashed underlining indicates nonmimic oriole. Blank: neither Philemonnor Orioluspresent. pairsof coexistingnonmimic orioles and friar- months, distributed over all months of the year and birds (Australia),friarbirds living outsidethe over 9 yr from 1964 to 1981. range of orioles(New Britain, Umboi), and oriolesliving outsidethe rangeof friarbirds PATTERNS OF MIMICRY (Java,South Africa, Germany). The Meliphagidae, or honeyeaters,originat- ed and (like marsupials)underwent an adap- STUDY MATERIAL AND STUDy SITES tive radiation in the Australian region and At the American Museum of Natural History, Brit- producedthe morphologicaland ecological ish Museum (Natural History), and Museum Zoo- equivalentsof numerousfamilies elsewhere logicumBogoriense I examinedall specimensof (Keast1976). Friarbirds, the largestmeliphag- friarbirds, all specimensof oriolesof the Australian ids, areconvergent on the predominantlyAfro- region(including Wallacea), and selectedspecimens Asian Oriolus in size, diet (nectar, insects, soft of all extralimital oriole species. Field observationscovered the following areasand fruit), nest (woven suspendedcup), and hab- species.New Guinea(Fly River, OriomoRiver, Kar- itat (tree canopy).In adult plumagethe Afro- imui Basin,Astrolobe Bay, Huon Gulf, Torricelliand Asian orioles are mainly yellow and black Bewani mountains, Meervlakte, van Rees Moun- (Frontispiece:right-most two birds of top tains, Gauttier Mountains, Onin Peninsula, and vi- row), very unlike the mainlybrown friarbirds. cinitiesof Port Moresby,Popondetta, Wewak, Van- One speciesgroup of Oriolushas invaded imo, and Jayapura): Oriolus szalayi, Philemon and differentiated in the Australian region, so novaeguineae,P. corniculatus,P. citreogularis,P. mey- eri, and Pycnopygiusstictocephalus; Australia (Ath- that the orioles of the Oriolus [bouroensis] su- erton Tableland and vicinities of Canberra, Sydney, perspeciesand friarbirds of the Philemon Brisbane,and Cairns):O. sagittatus,O. fiavocinctus, [moluccensis]superspecies now shareeight is- Philemonnovaeguineae, P. corniculatus, P. citreogular- lands or island groups.These are Ceram, Hal- is; New Britain (Cape Gloucester)and Umboi: P. mahera, Bum, Tenimbar, Wetar, Timor, New cockerelli;Java (Bogor):O. chinensis;South Africa (KrugerPark): O. larvatus;Germany: O. oriolus. Guinea and neighboring islands(Waigeu, Sa- Observationsin the Australianregion totalled 25.5 lawati, Batanta,Misol, Japen,Aru), and north- April 1982] OrioleMimicry of Friarbirds 189 TABLE 1. Adult plumage of coexisting friarbirds TABLE 1. Continued. Philemon [moluccensis])a and orioles (Oriolus [bouroensis]).b AUSTRALIA. P. buceroidesand P. novaeguineae. CERAM. P. subcorniculatus. Olive-brown dorsal- As on New Guinea. O. fiavocinctus(streaky yellow- green, with black in wing and tail) and O. sagittatus ly, yellow-brown ventrally, breast and axillariesyel- (olive back, streaked on white below) dissimilar. low. Head markings: grey color; streaked crown; Dissimilar. small bare or sparselyleathered circumocularpatch. O. forsteni.Same. Virtually identical.½ • Friarbirdpopulations are describedwith respectto thoseof other islands,to illustrategeographic variation. HALMAHERA. P. fuscicapillus. Medium-dark • Oriole populationsare describedwith respectto the friarbird of brown, darker dorsally; the darkest population. No the sameisland, to illustratemimicry. streaks and no markings except for small bare cir- •' The wordsin boldfacesummarize the closenessof mimicry. cumocular patch and slightly grey throat; the most uniformly colored population. O. phaeochromus. Same, except: slightly darker ventrally, throat not greyer, lacks circumocularpatch. Closely similar. BURU. P.m. moluccensis.Body as on Halmahera, ern Australia(see Fig. 1). From islandto island except paler. Head markings: pale hind-collar, su- perciliary, and throat; streaked crown and throat; these oriolesshow great geographicvariation bare black facial patch. O. b. bouroensis.Same, ex- in plumage,and so do the friarbirds.Some are cept:has black featheredpatch correspondingto bare nearly uniform brown, others paler ventrally; skin of friarbird; side of throat streakJer.Closely darknessof colorationvaries; pale completeor similar. partial collars, dark ear coverts,dark mous- TENIMBAR. P. moluccensis timorlaoensis. As on tachestripes, pale superciliarystripes, streaked Buru, except: lacks pale superciliary; obscure dark crownsand throats,and olive or yellow washes ear-coverts and moustache. O. bouroensisdecipiens. Same, except: has black feathered patch correspond- may be present or absent; and one or more ing to bare black skin of friarbird; crown slightly black patches of varying sizes, consisting streakJer.Closely similar. either of bare skin (Philemon)or of solid feath- WETAR. P. buceroidespallidiceps. As on Buru, ex- ering or streakedfeathering (Oriolus), occur on cept: paler brown; throat paler, almost white; bare various parts of the head (Frontispiece,Table blackfacial patch larger; has bare black patchon side 1). This geographicvariation is largelyparallel, of neck; has black moustachefeathering adjacent to bare black facial skin; has bill knob. This population however, such that on all islands except Aus- and the Timor one are the palest populations. They tralia the oriole and friarbird resemble each are also the ones with the boldest facial pattern, due other, often to such a stunning degree that to the contrast between the black facial skin and specimensheld in the hand can be distin- moustacheand