134 SOUTH AUsTRALIAN ORNITHOLOGIST, 21

THE OF KANGAROO ISLAND HUGH FOB,D Accepted August. 1976 Kangaroo Island is the third largest of Aus­ In the present paper I discuss morphological tralia's islands (4,500 sq. km) and has been and ecological differences between populations separated from the neighbouring Fleurieu of several species of honeyeaters from Kangaroo Peninsula for 10,000 years (Abbott 1973). A Island and the Fleurieu Peninsula respectively, mere 14 km separates island from mainland; and speculate on how these differences origin­ but the island has a distinct avifauna and lacks ated. many of the mainland species. This paucity of DIFFERENCES IN PLUMAGE species has been attributed to extinction after The Kangaroo Island population of Purple­ isolation and failure to recolonise (Abbott gaped was described as larger and 1974, 1976), and to lack of suitable habitat brighter than the mainland population by (Ford and Paton 1975). Mathews (1923-4). Brightness of plumage is a Nine species of honeyeaters are resident on very subjective characteristic, and in my opinion Kangaroo Island. The Purple-gaped Honey­ Purple-gaped Honeyeaters on Kangaroo Island eater Lichenostomus cratitius (formerly Meli­ are, if anything, duller than mainland ones. phaga cratitia) was described as a distinct sub­ Condon (1951) says that the gape of this species by Mathews (1923-24); and Keast species is invariably yellow on Kangaroo Island (1961) mentions that six other species differ in instead of lilac, although he later comments a minor way from mainland populations and that lilac-gaped individuals do occur on the may merit subspecific status. These are all island (Condon 1969). The "gape" which given subspecific names by Salomonsen (1967). Condon discusses and which gives the its NOVEMBER, 1916 135 Kanzaroo Island differ in plumage from the name is, strictly, a wattle, a flange of 'engorged o 1 . mainland popu ations. skin extending back from the gape (sensu DIFFERENCES IN STRUCTURE AND stricto). Terrill (in Rix 1943) showed that the yellow wattle was an immature character, as ECOLOGY I have sufficiently large samples of measure­ the wattles of four captured near Monarto ments of five species of h~meyeaters fro;n in late spring changed from yell?w to purple Kangaroo Island and the mainland for states­ by the following winter. Even. If. th~ yello.w tical analysis (see Table 2). Only small numbers wattle is an immature characteristic, It IS ~tlll possible that the Kangaroo Island populatIon of Tawny-crowned Phylidon'J.!ris melanops and differs from the mainland one m that the White-eared Honeyeaters Lzchenostomus leu­ development of the purple wattle is .delayed or cotis and Red Wattlebirds Anthochaera carun­ even suppressed entirely in som.e .blr~s. The culata were measured, showing no 'apparent differences between island and mainland popu­ retention of immature characteristics IS shown by 'other species or popu!ations of bir?~ on lations. islands. Male Darwins Finches, Geosplzm~e, Purple-gaped Honeyeaters on Kangaroo of the Galapagos Islands show a progresslVe Island have slightly shorter beaks and longer loss of the black adult male plumage and re­ wings than the mainland population (t test, tention of the grey-brown female and immature p { 0.05) . They have also undergone an plumage. In Tasmania the endemic .F?rty­ ecological change, as they occupy forest, wood­ spotted Pardalote Pardaloius ouadriginius land and mallee-heath habitats on Kangaroo closely resembles an immature Spotted Pardalote Island, but only mallee-heath on the mainland P. punctatus from which it presumably evolved. (Ford and Paton 1976). The increased range I have noted the wattle-colour of Purple­ of habitat on Kangaroo Island may result from gaped Honeyeaters mist-netted in Flinders the absence of the Yellow-faced L. chrysops Chase National Park, Kangaroo Island, and at and White-plumed Honeyeaters which occupy Braendler's Scrub, Monarto, in the Murray forest and woodland habitats on the mainland. Mallee between September, 1974 and July, As both of these species have shorter beaks 1976. The numbers of individuals with wattles than the Purple-gaped Honeyeater, the reduced of each colour from the two areas are given beak length of the Latter species on Kangaroo in Table Ia, The proportions of the two colours Island may be the result of Character Release are the same in both areas; so the yellow wattle (convergence in morphology towards an absent is probably an immature characteristic which is competitor, see Grant,1972). not retained longer on Kangaroo Island than The Brown-headed Honeyeater Melithreptus on the mainland. This is consistent with breoirostris on Kangaroo Island has a signifi­ Terrill's observations, but there is another pos­ cantly longer beak and wing, and is heavier sible explanation. Fuscous L. fuscus and than on the mainland. Keast (1968a) suggests White-plumed Honeyeaters L. penicillatus show that this is due to an increased amount of bark­ a change during the year in the colour of their feeding by this species on Kangaroo Island, in oral flange, which is mostly dark in late winter the absence of bark-feeding tree creepers and spring, and pale in summer and autumn. Climacteris and sittellas Daphoenositia. The colour may indicate breeding condition if This increase in size, especially of the bill, it is dark in breeding birds and pale in non­ and development of the tree-creeper-like;feeding breeding ones (Dow 1973, 1975, and Lane ecology is shown to an even greaterextent by 1974). The same may be true of the wattle the Strong-billed Honeyeater M. ualidirostris of in the Purple-gaped Honeyeater, with yellow Tasmania (Keast 1968a, Thomas m.s., and indicating not only an immature but also a non­ pel's. obs.). Keast (1968a) regards the Black-' breeding adult. Recapture of a bird showing chinned Honeyeater M. gularis as the ancestor the appropriate colour-change (purple to of the Strong-billed; but, in my opinion, the yellow) would be necessary to confirm this. Brown-headed Honeyeater, particularly on The numbers of birds with yellow and purple Kangaroo Island, far more closely resembles wattles in each season are shown in Table lb. the Strong-billed in its behaviour and calls. In More birds with yellow wattles were caught addition the Brown-headed Honeyeater occurs in summer and autumn than in winter and throughout southern. Victoria and on the Bass Billing (p .( 0.05, Xl test). Although the breed­ Strait islands, whereas the Black-chinned ing season of this species is not well known, occurs only to the north of Melbourne in it is possible that wattle-colour is related both Victoria. to age and breeding condition. In the New Holland Honeyeater None of the other species of honeyeaters on nouaeliollandiae, in both sexes of the Crescent 136 SOUTH AUSTRALIAN ORNITHOLOGIST, 21 H~ney~ater P. pyrrhoptera, and in the Eastern Interspecific competition is often considered Acanthorhynchus tenuirostrls there as a force bring!ng about changes in island are slight differences in measurements between populatlOn~ of birds, A; species may change island and mainland samples. However these morph~logIc~l1y01' ecologIcally when a potential show remarkably consistent trends in these three competitor IS absent. This change is usually species. The island populations all have signific­ but not always shown as a convergence towards antly longer beaks than the mainland ones; they the ab~ent competitor, or a divergence away all have s~ort~r wings (significant in all except Spmebl~ls); from It whe,: the two species are present female and are all slightly lighter together. ThIS phenomenon of character dis­ !han their mamland counterparts (significant placement is discussed at length by Grant I~ all except male Crescent and female Spine­ (1972). Although competition or lack of it bills). Campbell (1905) described the first two may h avebeen een Importantvi in ,changes in the, as because of their longer beaks. He Purple-gaped and Brown-headed Honeyeater, gave the Spinebill a subspecific name because all of the long-beaked honeyeaters of the neizh­ it was smaller and paler than Victorian birds, bouring mainland occur on Kangaroo Island but does not say how many individuals of each (3 species of Phylidonyris, 2 Anthochaera and species were measured. Paton (pers. comm.) 1 Acanthorhynchus)" so there would seem little says that from coastal Victoria have opportunity or necessity for convergence or beak lengths similar to those of the Mount divergence as a result of increased or reduced Lofty Ranges, but that those from mountain ~ompetition. Another reason for changes on regions have longer beaks and are similar to Islands, probably the most obvious but often more northern samples (Disney et al. 1974). over-looked one, is that the environment on The biogeographical laws of Bergmann and the island is different from that on the main­ Allen state that of one species become land. If Kangaroo Island is considered broadly larger and have shorter extremities in colder there are two main habitats; a rather stunted regions. This is contrary to what has happened dry sclerophyll forest with E. baxteri and E. on Kangaroo Island, which is cooler than the cosmophylla, and a mal1ee-heath with E. diver­ Fleurieu Peninsula and yet these three species sifolia and E. rugosa, habitats also found on of honeyeaters are smaller and have longer Fleurieu Peninsula and the lower Murray beaks. Keast (1968b) showed that nomadic Mallee respectively. On .Kangaroo Island there or migratory species of honeyeaters tend to have are also limited areas of tall woodland with longer wings than more sedentary species. E. cladocalyx, E. [asciculosa and E. huberiana Perhaps the more maritime climate of Kangaroo simi.lar to, but taller than, that found on Eyre Island leads to a more predictable food supply Peninsula, and less necessity for movement among the On the mainland the most important sources honeyeaters. Certainly in the autumn and early of nectar for honeyeaters are winter of 1976, when food was scarce on the (especially E. leucoxylon) with 53% of the mainland, honeyeaters were finding sufficient 2,900 observations of all species of honeyeaters food on Kangaroo Island to breed. feeding on nectar, some heaths such as Astro­ The change in beak lengths of the New loma conostephioides (10% of all records) and Holland, and Crescent Honeyeaters and Spine­ (10% of all records) (Ford and Paton, bill is particularly interesting, as this character in prep.). Eucalyptus appears to be far less is closely related to the feeding ecology of a important on Kangaroo Island and Correa (3 species. species), Adenanihos and Banksia seem to be Populations may diverge for genetic reasons the major nectar sources (pers. obs. and alone: when their numbers are low the popula­ McWilliams 1973, Honours thesis, Department tion as a whole only contains a sample of the of Zoology, University of Adelaide}. It is very genes of a larger population. The smaller the hard to observe honeyeaters feeding on the sample the more the average for a morpho­ flowers from low bushes on Kangaroo Island logical characteristic is likely to differ from because the vegetation is so dense. A more that of the original population. This seems an representative picture of which flowers the birds unlikely explanation for this distinctness of the are feeding on can be gained from collecting Kangaroo Island populations, because, at and identifying pollen from birds caught in present anyway, they must number some tens areas where a range of plants is flowering. In of thousands of individuals of each species. Table 3 1 have compared the numbers of Also the similarity of the trends in these three individuals of each species carrying pollen of species suggests a common directional force a range of species of plants on the mainland rather than random genetic drift. (from Paton and Ford, 1977) and Kangaroo NOVEMBER, 1976 137

Island. The data from the mainland are not account for the increased beak lengths of these strictly comparable, as birds were captured close species. A slight reduction in wing length to specific flowering trees or bushes to collect might be the result of less necessity for local evidence that birds transfer pollen of a movements on the island. particular species of plant, rather than being ACKNOWLEDGEMENTS I am grateful to David Paton and Neville Forde "for captured in an area where a wide range of criticising this manuscript. and thank the South Australlan National Parks and Wildlife Service for permitting me plants was in flower, as on Kangaroo Island. to capture birds in National Parks, and Mr. BraendJ!,r. of This would tend to underestimate the most im­ Murray Bridge and the Monarto Development Commisston portant plants, such as Eucalyptus, so that the for permission to work art; Braendler's Scrub. REFERENOES difference between island and mainland is AJbbott, I. 1973. Birds of Bass StrU\t. Evol~ti~n. and ecology of the avifaunas of some Bass StraIt I.slan,!s, probably greater than suggested by the results. and comparisons with those of Tasmama and Vlctona. The Table shows the importance of Correa, Proc R. Soc. Vict. 85, 197-223. Abbott: I. 1974. The avifauna of Kangaroo Island and and Banksia, and less emphasis on causes of its impoverishment. Emu 74. 124-134. Abbott I. 1976. Is the avifauna of Kangaroo Island Eucalyptus, on Kangaroo Island relative to the impoverished because of unsuitable habitat? Emu 76. mainland. Longer-beaked birds could be more 43-45. ' Campbell, A. G. 1905. Report on -the birds of Kangaroo efficient at feeding on the tubular flowers of Island: a comparison with mainlan.d forms. Emu 5. 139-145. . Adenanthos and especially Correa, and also Oon.don, H. T. 1951. Notes on the birds of South Australla, possibly on Banksia which 'has long stiff styles occurrence, distribution and Ita:,

TABLE 2 The mean, standard error and sample size for beak length, wing length and weight in five species of Honeyeaters from Kangaroo Island and the neighbouring mainland.

Beak length (mm) Wing length (mm) Weight (gm) mean.± S.E. (no)

Brown-headed KI. 14.3 + 0.22(20) 72.1 + 0.53(19) 17.0 + 0.87(14) Honeyeater main. * 12.9 + 0.13 (29) *67.3 + 0.49(29) * 13.9 + 0.80(22) Purple-gaped KI. 14.3 + 0.17(40) 81.8 + 0.53(40) 19.7 + 0.35(36) Honeyeater main. * 15.0 + 0.20(19) * 80.0 + 0.51(24) 20.3 + 0.74(16) Crescent M KI. 18.9 + 0.18(38) 69.2 + 0.28(38) 14.7 + 0.36(14) Honeyeater main. * 18.2 + 0.19(38) * 70.8 + 0.45 (82) 15.4 + 0.32(82) F KI. 17.2 + 0.15(82) 62.3 + 0.28(82) 11.9 + 0.87(15) main. * 16.7 + 0.18(22) * 68.9 + 0.29(22) * 12.9 + 0.27(19) New HoIland KI. 20.7 + 0.12(82) 74.0 .± 0.43 (82) 19.6 + 0.40(86) Honeyeater main. * 19.6 + 0.10(86) * 75.9 ± 0.40(86) * 21.0'± 0.26(58)

Eastern M KI. 28.8 + 0.15(58) 63.8 + 0.28(58) 10.6 + 0.17(33) Spinebill main. * 23.1 + 0.25 (1~) * 67.1 + 0.33(14) * 11.5 + 0.46(10) F KI. 21.0 + 0.24(35) 59.1 + 0.42(35) 9.4 + 0.17(26) main. * 20.0 + 0.37(10) 59.5 + 0.45 (10) 9.3 + 0.43 ( 6) * indicates a significant difference between the means from the two areas, p <0.05.

TABLE 3 Numbers of birds of each species from which pollen samples were taken, carrying poIlen from a range of flowers on Kangaroo Island and the mainland. Adenanthos Banksia Correa Eucalyptus GreviIIea Others KI. main. KI. main. KI. main. KI. main. KI. main. KI. main. Purple-gaped 4 7 6 3 1 2 5 3 Brown-headed 2 1 3 3 1 4 1 3 Crescent 14 3 17 24 10 7 3 8 2 1 20 New HoIland 34 13 26 68 18 53 8 59 4 25 84 Tawny-crowned 1 1 1 1 10 5 10 3 Eastern Spinebill 22 1 17 11 25 11 2 4 2 13 1 4 9 3 5 4 3 3 TOTAL 78 19 75 116 62 90 14 86 4 46 8 129 % 33 4- 32 24- 26 19 6 18 2 10 1 26