June. 1981 P. Park: Colour-banding Breec.lingWelcome Swallows 41
Acknowledgenrents Refcrence 'The I wish to thank D. Milledge for carrying our Ros le1, l. ( 1965), Lifc Flistor_v of 1he Superl.r the_lutopsy on M2. D. Purchase,D. Serventy, f]fttc \\'rcn Nlalurus t't'aneu.t', Etnu 64'. 251-2g7.' S. Ci. Lanc ancl A. Leishman are thanked f6r tlteir help and guidance.An apology rnust bc givcn.toall the peoplenot rnentionedspecifically. cspcciallyrly fanrily, for whose help I am verv "Stoney". P. Park. Campania. sratcful. Tasnrania.7202.
MixedSpecies Flocks in a Dry Sclerophyll Forestin Autumnand Winter
NEIL HERMES
Mixed . species feeding flocks were studied in dry sclerophyll forest at Blacl< Mountain Nature Reserve, Australian Capital Territory.'foraging' Twenty-three spbcies weie ooserued in mixed flccks. .Species are grouped according to patern and details ot tfre compoiition of the llocks is oiven.
Mixecl speciesflocks have been studied irr Cullen ( 1972) have showir in experimental nrany parts rrf the rvorlcl e.g. Ceylon (partridge studicsthat nrixedspccies llocking mav increasc and Ashcrotir 1916). Sarawak (Croxall 1976), thc arnountof intcripcc!ficlcirrniitl ol: potcntial Kashrnir ( Macdonald *GosslCustard and Henderson 1977). food tou..".. Llck ( 1968) and Patagonia (Vuiller-rnrier (Davis 1967), Brazrl ( 1970) sugges-tedar.r antipreclator advantage to 1916). Peru (Munn and Terborgh 1979) ancl nrixedspecies flocking behaviour. Arizona (Ar-rstinancl Linwood Smith 1972) ancl In this study the aim was to determinethe shown to occur in a rvicl: range of habitats ancl extent to which mixed speciesflockine occurred to. vary in the nunrbcrs. speiics ancl foraging in Australian birds in a dry scleropilyil forest behaviourof birds present. Macclonalclancl tlenl outsidethe breedingseason. Also, it-was hoped derson (197'7) stated that this variation makes the study would indicate rvhich speciesformecl it diliicult to devise a general hypothesisto ex_ mixed speciesflocks and how theie flocks rvcrc plain the existenceof mixed specG flocks. Morsc slructured. There are few published recorclsof ( I970 suggcsteclthar ) ceriain species rvithin thisbehaviour in Aus;traiianbirds (Canrrorr1934, nrixed spe*ciesflocks reduce comperirion by feed- Scdgrvick 1949) . Bell ( in press) has exarrrinccl ine in diflerent sites to the onei used bv other mixed speciesflocking in the s:lme location as :lpecicsirr the flock. Krebs, MacRobeits and this study. 42 N. Hermes: Mixed Species Flocks Corella 5 (2) Methods the Yellorv-facedHoneyeater, was still moving __'fhe four study areasin the -52I hectareBlack through the area in April. The Golden Whistleri Mountain Nature Reserve in the Australian a winter migrant, was recordedin larger numbers Capital Territorv were located in the north and irr April than during the resr of rlri studr. No wcst of the reserve..Th,.y hacl northerly and birds^of. prey werc observeddurine the study. wcsterly aspccts.Their altitucle ranced-ran._qed beiween Of all the observations,304 or a6out g9lowerc 620-680 ntetresand the topo-rraphy from nradeof birds in 53 mixed speciesflocks. Twenty_ rrndularingro steep.The hoi.rh6rnand'western three species were observecl in mixed soecies sroesoI tne reservewere dominatedbv various age classes of Eucalt,ptrr,rrrr,r.sri with srnaller rrreas of E. polyantltenrcs and E. blakeh,i. Thc TABLE I dorninant lree speciesin the study areas was !-.. ro.rsii although E. tttacrtrln.n<.lia ancl E.ro- Thc nunrber of mixed (oryu.s species flocks observed Iisted c:upres.siformi.roccurred in most plots. against lhe number of species presenl. Three different census nrethods rveie usecl: the transect method (where Number of Species of mixed species the observer moves ,_Number flocks at given speed recording all birds seen within a 4 20 siven clistancefrom a track), the point quadrat l0 (where nrethod all bird.sobserved by a staiionary 6 t) observer are recorded for a given t0 tinre) ancl the 8 a searchingquadrat (in method rvhich the observer 9 -l searchesa marked area for a given time). These threc census ntethods were b-einccontpared as trf.a rviderstudy (Hernrcsl977;. The'clatafor thls studyhave been pooled from the threecensus TABLE tecnnlques. 2 -f A niixecl speciesflock w.asdefined as four or l.rc.Jrercentage of mixcd species flocks in *,hich each rnoredifferent species occurring within specles \r'as presetrt and the mcan number of individu_ 50 rrretres als of each specics observed ()t oltc another ancl rrroving together. in mixcd species flocks. When a I he mean $as obtaincd by dividing the total number of mixed speciesflock irrrli.uidualsof species was obs;rvej the number of ,a bbserved' bv the "u-ire, nf n()cKs ilt $htch bircls of cach specieswas recorded.The number that species ^$as prcscr)t. Specics arc shonn in ordcr perccnlage. 1or each specieswas the maximum seen at any of orrc tinte together.The number recorded for anv oue species is therefore Species Percenlagc Mcan number of the rninimum number of flocks presentin the flock. individuals in flock ButT-rumped Thornbill 7l )./ White-throated Treecreeoer 68 1.2 Results Golden Whistler -).) t.8 Scarlet Robin 47 1.5 During the fifteen rveek 'censusingperiocl frorn Anril to Grel- Fantail t1 1.9 Augr,rst1977, 140 hours of Supcrb Fairl'-Wren 40 were com- Striated Pardalote plcted, 38 -, .1 and 3 80-5 observationswere made. An Striated Thornbill observation 30 4.1 was each separaterecord of an in_ Varied Sittella 28 6.3 dividual or group of i;dividuals of the same Gre-l Shrike-thrush 28 t.l spc.cies.Thirty-nine species Spotted Paradalotc 2l 1.4 were observed of Brou n Thornbill lvlrich twenty were t9 2.7 knoun to be breedins resi_ Ilastern Yellow Robin l5 1.0 dents. Scicntific nan.resof species are giien in Speckled Warbler ll ,: Appcndix l. Ycllou-faccd Holleveater 9 All srurrrner White-eared Honereater 1 . nligrantslrad lefr rhe study areas Eastern Spinebill hclorc the strlrt o[ censusingexcept for the Lea_ Silverel'e ^ rlcrr. Flycatcher, which wa*s onlv recorded in Crimson Rosella April. and the Fan-tailed [-eaden Flycatcher Cucko-o, Black_faced Australian Cuckoo-shrikeand Raven 2 Grev Fantail. Srnallnumbers White-naped Honeveater 2 of these species often over-winter in the Can_ Picd Cuirauonr z b:'rra area (Frith 1969). One passagemigrant. Unidentified 2 June. 1981 N. Hermes: Mixect Species Flocks 43 llocks althoughsoure of thesemay have only becn than 759b of the composition of a flock conte soincidental. The average number of birds from only one group. The most comnton merlber,; observedin each flock rval 16.2. The ranse was ol mixed speciesflocks are insectivorous. 6-39 birds. The number of species presint in each flock is shown in Table l. The number of flocks in which each species was present ancl Discussion the averagenumber of individuals of iach species Mixed species flocks contained 8/r, of all prcsent is shown in Table 2. Specieswtrich dict clbservationsmade during this studv and there- not occur in mixed species flocks are listed in fore are an important infl"uenceon tire behaviour Appcrrdixl. of many birds in the study area. It is possible The speciesoccurring in mixed speciesflocks that rnixcd speciesflocks may only have advant- were arranged into groups based on their pri- ages for son.respecies and perhaps, although rnary food preference and foraging patterns there is no evidencefor it here. onlv at certain accorcling to Frirh ( 1969) (Table 3 ). these times of the year. However, since some atJvant- figures give a misleading indication of the re- ilges may be subtle, these reirsonsmay not vet gularity with which the aerially feeding species bs apparent. occurreclin mixed speciesflocks since the Grey The mean number of birds in each flock in Fantail largety left the area durinq the middle this study (16.2) is similar to the figure of 14.6 of winier. nighty-six percent of al! irixed species four.rdin post-breedingrnixed insectivorousbird llocks contained representativesof three or more flocks in woodlands in Arizona ( Austin and of Groups A-E. Only on live occasionsdid more l-incfwood Smith 1972'r. Thev srate tlrar these
TABLE 3 -fhe compositiott of fbcks b_r'foraging pattern of species. The species are grouped according to foraging pattems given by Frith (1969).
Group Foraging pattern Species No. of flocks in ri hich group *.as prescnt Eastcrn Yellol Robin Insectivorous species of Superb Fairl-Wren lS (919o) the ground and los bushes { Speckled Warbler LBirff-nrmped Thornbill lnseclivorous species of Varied Sittella l8 t721al trcc trurrks. { \\'hite-throated Treecreeper Striated Thornbill Instclivorous species of Spotled Pardalote ( outer tree foliage. .l-5 669i ) { Striated Pardalote
Insectivorous species of Goldcn Whistler .15 (66cL shrLrbsancl lorl bushes. { Bro* n Thornbill ) Insectivorous spc-ciesof Scarlcl Robin 33 t629a\ thc ground. { Crey Shrike-thrush Insectivorous acrial Leadcn Fllcatchcr 22 t1lo1o\ fccdcrs. { Crcl Fantail ( Crimson Rosella Yclios-faced Honeyeatcr \\'hite-eared Honeveater \\'h ite-naped Hone-,-eater Othcr fr.L'(lini:l\ pcs ( Eastem Spinebill l-5 28o,'o) lSilvcreve I Picil Curratong LI Aus;lralian Raven 44 N. Hermes: Mixed Species Flocks Core,la5 (2) types of flocks from regions .tentperate are re_ It was not clear whether this was due tcr thc nrarkably in ancl .similar -size su_sge-stthere may leading birds separatinqfronr the flock or he urr oplinrum size due for suchflocG. to new individualsjoining the flock. A pattern of vertical structuring of nrixed adaprive significarrceol lnixed species species flocks rvas observed. ^ Tl. T-his ii shown b\ flockingbehaviour has been consideredby many the fact that 86Vo of all the flocks had repre- authors (Crook 196-5,Macclonald and Hender_ sentativesof at least three of the foraging groups son 1977, Vuilleurnier1967, Partriclgeand Ash_ A to E (-fable 3). In addition to theiuirbers or croft 1976, Croxall 19i6, Ruberrs'ieinet. al. rndividuals()r any one group only rarelyconsri_ 1977, and Morse 1970). In this study rhere lutcd morc rhan 7-5? of the total floak. tr is was no evidencetcl indicate that increas-edpro_ possible that whatever the function of mixed te,.clion predators rvas a major advantagc specresflocks the regular .fronr vcrtical structuriugbv of flockingas postulatedbv someof theseauthois. lts contponentspecies may be important.lt ha, Alternatively, it has been proposed that rnixed be that the function of the mixed speciesflocii speciesflocks increasethe elliciency of foraging can only be achieved if a certain number of of irrdividual birds by reclucinginciividual com_ indiviclual birds occupy at least a ntinilnunt petition (Morse l97O) or by" enabling parchy rll.lttlbcrtrf I'eedingzonL.s. Arthough the pattell fo^od supplies to be ntore eflectively-utilisei ()l verticalsrructurins of the flock nlay bc .sinlrlar (Crook 1965). The la-tter,explanation is sup- in lorestsof sinrilar itructure, 'is the speiies occupy_ ported.by rhe linding of this study that there iug.each fora_eing zone may changi with distance a verttcalstructuring of the flocks. an0 tlnle. Such a flock would be more elficienrin finding and expl References NlacDonald, D. W. and I). G. Hendeison, (1977), 'Aspects of the behavi APPENDIX I I.ist of species observcd on stud] plots in the Biack Vlountain Nalure Re:;enc during April 'RccommcnCei! to Au_qust 1977. Scientiflc anil common namcs follori the English names for Arrstralitut birds' RAOU 1978. Asterisk mark those ,spccies* hich \\crc '()t rec.rtled in nrixed spt'cics lloc!:s. Mancd jubata Duck C-ltenonetta Striated Thornbill A(antlti:a litreata Painted Button-quail Turnix varia Varied Sittella Daplroenosi t la clt rl,.sopiara Common Bronzewing Phaps dralcoptera lVhite-throated Gang-gang Cockatoo Callot epltalon ftntltria!trnr Treecreeper Clintacteris Ieucopltaea Australian King-Parrot Alislerus scapularis 'r' Rcd lVattlcbird (-'rimson A n thot'ltae ru (0r un( u Iu I u Rosella PIatyt'ertu.s elegans Yellow-faced Eastern Rosella Plattcertus exintiu.s Honeyeater Liclteno.slomu:; cltrysopt Itan-tailed Cuckoo C uculus Pyrrltopltanus lVhite-eared Honeveatcr Lit'Jtcttostotttttr leuu;li ; l,a*ghing Kookaburra I)acelo noyaeguineae 'r lJrowrr-headed lilack-faced Honeyeater l\,1el i t lt re p tu.s bret' i rost ri t Cuckoo-shrike (- orat i n a noy uelt ol Iand i ae lVhite-naped Honeyeater i\.1el i t ltra pt u.s ! unat Rlackbird u.s 7'urdu.t tnerula liastcrn Spinebill ,1cortthorltyncIt Scarlet u.t Robin Pe trrtita trtul licolor tctltiro.ttri.\ Flastern Yellow Robin Eopsaltrio austrelis Spotted Pardalote I'ardalo t u.s purr( l0t u.\ Golden lVhistler I' ac lt yce p Itala pet torol i.s Striated Pardalotc Pardalo tus .\t riatu.\ (Jrcy Shrike-thrush ('o!IuricincIa lnrmonica Silvereye Zosterop.s laterali.s l.eaden Flycatcher trlfia:gra rubecula !' Common Starling ,Sturnus vulgaris Grey Fantail r' Rhipirlura luliginosa lVhite-rvinged Chough Corcoror melanorhc:ntpir,tt Superb Fairy-wren '' tr'l aluru.y c).aneu.s Austrafian Magpie () Speckled 1'ntnorltino tibi< :rt Warbler Sericornis sagittatu.s Pied Crrrrawons ,\lrepera graculina llrown Thornbill :' .4t'ontlti1a pusilla Grey Currawong Strepera ver.sitolrtr llrrtf-rrrrnped Thornbitl A cantltiza reguloide.s Australian Raven Crtryus tttntnoitles