Corella,1993, 17(4): 107-110 INTERSPECIFICAGGRESSIVE BEHAVIOUR BETWEENROBINS AND OTHER BIRDS IN EUCALYPTFOREST DOUG ROBINSON Department of Ecology and Evolutionary Biology, Monash University, Clayton, Victoria 3168 Present address: 28 Bath Street, Mornington, Victoria 3931 Received16 November1992 Recordswere kept for 328 interactionsbetween ScarleVFlame Robins and other landbirdsat a site in south-easternNew SouthWales. Fifty-seven per cent of interactionswere betweenrobins and otherground{oragers, particularly with Jacky Winter (41 %). Bark{oragers,foliage{oragers and honey- eaterswere rarely,if ever,attacked, except when they came near nestsof robins.Honeyeaters were responsiblefor 57 per cent of the attacksdirected at robins. INTRODUCTION STUDY SITE AND METHODS Many speciesof Australian honeyeater aggres- Thc study was carried out at a site of approximately 300 ha sively defend food resources and space from near Nimmitabel, on the Southern Tablelands of New South intruders; not only from conspecifics but also Wales (36'46'5, 149"22'E). The site consists of open Eucalyp tus viminalis, E. pauciflora from a wide range of interspecific intruders (Dow forcst and some grassland, and is described in more detail elsewhere (Robinson 1992). 1977; Paton 1980; Loyn et al. 1983; Woinarski 1984). Their aggressive behaviour has been Between March 1984 and March 1986, individually colour- described as'remarkablv indiscriminate' (Dow banded Scarlet and Flame Robins were followed for oeriods 1977) and extends to species of 5-45 minutes, during which time the frequency and duration as ecologicalli dis- of all interspecific disputes, similar as the identity of the aggressor and fairy-wrens, finches and grebes (Dow identity of the bird being attacked (hereafter termed 'recipient') 1977;Paton 1980). were recorded. Possible causes of the aggressive behavrour were noted whenever possible. Records of interspecific aggression among other Australian passerinesare few. Interspecifi- RESULTS territoriality, nest-site defence or dominance behaviour have been recorded for some species Twenty-eight speciesof bird were involved in a of robin, whistler, treecreeper, pardalote and total of 328 interspecific interactions with Scarlet/ corvid (Rowley 1973;Erickson I974; Noske 1979; Flame Robins at Nimmitabel - 16 species with Loyn 1980;Debus 1982;Woinarski and Rounsevell Scarlet Robin and,23 species with Flame Robin 1983; Robinson 1989a). Other studiesof sympatric (Table 1). For those interactionsin which Scarlet/ species of fantail, whistler, fairy-wren and Flame Robins were the aggressor (n : 159), 80 pardalote conversely have reported- little or no per cent were with ground-foraging species,notably interspecific aggression(Rowley 1963; Woinarski with Jacky Winter (70%) and occasionally with and Rounsevell 1983; Cameron 1985; Woinarski Hooded Robin, Eastern Yellow Robin and Buff- 1987). Here I present information on aggressive rumped Thornbill. Only six per cent of attacks by interactions recorded between either Scarlet robins were directed at honeveaters (Table 1). Robins Petroica multicolor or Flame Robins Speciesthat were never. or iarely. involved in P. phoenicea and other speciesof bird in a forest aggressiveinteractions with Scarlet/Flame Robins environment in south-eastern Australia. I also despite being common in the study area included: discuss the possible causes of the observed Superb Fairy-wren, White-browed Scrubwren aggressivebehaviour. Sericornis frontalis, Striated Thornbill, Golden 108 D. Foblrson.' Interspecificaggression between robins Corella17(4) TABLE 1 Recordsof aggressiveintcractions betwecn Scarlet/Fla,ne Robins and other speciesof birds. Records are arrangedby frequencywithin the subsetsof honeyeaterinteractions. ground-forager inleraclions andinleractions with other specics. An aslcriskindicates that birds were displaccd from close to nests- Scarlcl/FlameRobin as Aggrcssor Recipient Sc Fl Sc Fl Total White-raped I loncycaret Melithreplus lundtus 2* 12 3',7 5I Whilc-cared Honeycirtc( Lichenos tomu! leuotis 2' 21 9 lit Ycll()\l'iaced Honeyealer Liche nono nus ( hrysops IU Brown-hc.rded Honcyc^rer M elnh rcptu.\ h ft | i /ost ris 22 New HollrDd I fo cyc?rier Phylidonyris ttovkhollanLlitl( t* 2 l I r,.rern Spinrhrll,4,.rrrthorh\ n, htt\I/ttut tostt i, I 114 J.rcky wintcr Mi./oe..i leuco I haeu 59 52 a) t1 Eastcrn Yellow Robin EoFaltria iustralis 11920 2+38ll Hooded Robin M.'/.?r.)dr!us ut:ulla td ,7 Buff rumped Thornbill Acunthizu rtguloitles I I Crcv Shrikc-rhnrsh aolturic iti ( lu ltunloni(u 2ll Willie WagtailRhrp rru teutophrys l2 -l Supcrb Fairy-wrcn M.rlurtls (f anetts I I 2 Yellow-runpcd Thornl\tll,4ca n th i za chryso h oa I I Richard s Pipit A/rll&s noruesk[undiac I I t5 {)t ey I: anI^il Rh ip i d ura Iu Iigun.vt 51*51 Stfiated Thornbill n..r ntllizu !inedtd 4'l 5 Dusky Woods\ivallow A nanws ..ranoPt(rus l, ] + Rufi)us Whistlcr P.r.r)cq haIa ruf v ?n tri s l, 2 LirughingKookaburra D rcelo novue guin?ae Silcred Kingfisher H.r1.:v0, rar?.ld l- Satio Flyc.rtchcr M_riagruL! anol?ucu Varicd Sitrella r.4ro.nosittu chrlso ptc ta Striatcd Pardrlotc P.r/-dak, us striatu \ Hor\llcld s Bronze-cuckoo air).1o.o.. t-t Ddrali.t Shining Bronzc cuckoo ( [r')ro.o.c]r /kiilr! Fan-tailerl Cuckoo Carvlu t p "-rrh op hanus PallidCuckoo C (ar{ pal/idlr f()t.\l.s 85 511 lll Whistler 1'arlr-lcrp lula pettoruLis,Rutous Whistler, 57 pcr cent were initizrted by honeyeatcrs, Red-browcd Treecreeper Climacleris erythrops, espcciallyby White-earedHoneycatcr and White- White-throated Treecreeper C. leucophaea, naped Honeyeater (Table l). A further 35 per Spettcd Pardaletc Panlulotus PLLnctalusan(l cent were initiatcd by ground-foragcrs,including Striated Pardalote. 14 pcr cent begun by Jacky Winters (Table 1) Some specics were only/mainly displaccd by Scarlct/FlamcRobins if thcy came within c. 10 m InterspqciRcintcractions occurred throughout of nests (Tablc 1). The robins also displaceclor the year (Table 2) but some seasonalpatterns scolded Pallicl Cuckoos. Fan-tailed Cuckoos, appcared to diffef between the two spccies of Shining Bronzc-cuckoosand Horslicld's Bronze- robin. Thus, Flame Robins interacted most often cuckoos that camc too close to ncsts. with Jacky Winters in winter.tnd spring.whilc For thosc intcractions in which Scarlet/Flame Scarlet Robins interacted most often with Jacky Robins wcrc the recipientsof the attack (n : 169), Wintcrs in autumn. September,1993 D.Robinson: Interspecificaggression between robins 109 DISCUSSION TABLE 2 As found by some other studies of interspecific Seasonaldistribution of aggressiveencounters between robins aggressionbetween insectivorousbirds (slassvold and other speciesof birds expressedas number of encounters/ 1978:Woinarski and Rounsevell hour. The smaller sample sizcs for Flame Robins in autumn 1983).ne"st-site and winter are due defence to thc birds'absence from the studv site was one cause of aggression between from late April to August. robins and other bird species. Interspecific aggression by robins towards cuckoos also Autumn Winter Spring Summer presumably represented nest-site defence or SCARI-t1TROBIN defence of young: one pair of Flame Robins Observation time (h) 37.8 34.4 21.'.7 29.1 played host to a Fan-tailed Cuckoo and cuckoldry Interactions with: of Scarlet Robins by Horsfield's Bronze-cuckoo All honeyeaters(n/h) 0.38 0.29 0.41 0.34 (Howe has been observed elsewhere 1932). How- All non-honeyeaters 1.6'7 0.26 0.88 0.31 ever, interspecific interactions between robins o Ground-foragers 1.46 0.23 0.'/3 0.10 and other insectivores occurred throushout the I Jacky Winter 1.26 0.06 0.6s 0.03 yea.r, just g9.t in the breeding season (Table 2), FLAMEROBIN and additional causes are needed to explain the Observation timc (h) 16.3 8.8 22.5 22.9 remaining aggressive behaviour. Interactions with: Mistaken identity has been proposed as one All honeyeatcrs (n/h) 0.r2 1.02 1.24 1.04 All non-honeyeaters 1.tl possible cause of interspecific aggressionbetween 3.52 2.18 1.00 o Ground-foragers 1.10 3.52 similarly plumaged 1.73 0.70 birds (Murray 7971; Savard o Jacky Winter 0.3i 2.13 1.38 0.39 and Smith 1987). It was an unlikely causeof the aggression directed towards male robins by honeyeaters and other species, given the bright- Buff-rumped Thornbill. The latter three species red breasts of adult males. However, it may all forage on the ground (Recher and Holmes explain why robins sometimes attacked Jacky 1985;Ford et al. 7986,pers. obs), and overlapped Winters, as Jacky Winters somewhat resemble at least partly with Scarlet and Flame Robins in female robins in appearanceand behaviour. Field their use of habitat and space(Robinson 1989b). observations, though, showed that robins Accordingly, the larger'Hooded and Eastern responded to nearby Jacky Winters much less Yellow Robins may have benefitted from displacing often than they responded to nearby robins, Scarlet/Flame Robins whenever they entered the implying that the robins were able to identify larger birds' foraging space; Scarlet/Flame Robins Jacky Winters and behaved accordingly. may have benefitted from displacing the smaller Instead, competition for food appeared to be Buff-rumped Thornbills from mutual foraging the mosl likely cause of interspecific aggression sites. Although interspecific aggression between between Scarlet/Flame Robins and JackyWinters. these specieswas recorded only rarely, it has been The Jacky Winter was one of the few other proposed that such occasionaldisputes may signify insectivores at the study site that pounced for prey interference competition between dominant and in the open forest. Its foraging behaviour and use subordinate species(Beaver and Baldwin 1975; of foraging space in winter and spring was similar Sherry 1979; Maurer 1984) and may lead to to that of the robins; each species tendins to avoidance of the dominant's foraging spaceby the forage in open forest and pouncing or snatcf,ing subordinate bird (Morse 1974; Beaver and fo-r prey on or close to the ground.