Behav Ecol Sociobiol (1996) 38 : 287–292© Springer-Verlag 1996Christine R. HurdInterspecific attraction to the mobbing calls of black-capped chickadees (Parus atricapillus)Received: 23 March 1995 / Accepted after revision: 28 October 1995Abstract The species and number of birds attracted toplaybacks of mobbing calls and song of the black-capped chickadee, Parus atricapillus, were compared.The chickadee vocalizations were played at abandonedchickadee nests, and the numbers and species of otherbirds that approached the speaker were tallied. Few non-chickadees were observed in the area when the song wasplayed. That significantly more birds approached thespeaker and displayed mobbing behavior during themobbing call playback suggests that black-cappedchickadee mobbing vocalizations carry meaning for atleast ten other avian species. This finding supports theidea that species subjected to the same predators in anarea may benefit by recognizing each others’ predatorcalls. This recognition may be facilitated by the similarstructure of different species’ mobbing calls and also alearned association of another species’ call with the pres-ence of a predator.Key words Chickadee · Mobbing · Interspecific ·Defense· CallIntroductionAlthough mixed-species avian mobbing is a widely rec-ognized phenomenon, few studies have identified whichspecies join heterospecifics in mobbing or quantifiedthe number of participating birds. Curio (1978) definedmobbing thus: “birds of one or more species assemblearound a stationary or moving predator (potentiallydangerous animal), change locations frequently, per-form (mostly) stereotyped wing and/or tail movementsand emit loud calls usually with a broad frequency spec-trum and transients.” Mobbing calls can communicatethe presence of a predator to heterospecifics as well asconspecifics. Marler (1957) reported that chaffinches(Fringilla coelebs) are commonly alerted to nearby owlsby greenfinch (Chloris chloris) and bullfinch (Pyrrhulapyrrhula) mobbing calls. Florida scrub jay (Aphelocomac. coerulescens) mobbing attracted northern flickers (Colaptes auratus); red-bellied woodpeckers (Melanerpes carolinus); blue jays (Cyanocitta cristata); northernmockingbirds (Mimus polyglottos); brown thrashers(Toxostoma rufum); loggerhead shrikes (Lanius ludovi-cianus); and rufous-sided towhees (Pipilo erythrophthal-mus) (Francis et al.1989). When Zimmermann and Curioattracted great tits (Parus major) with a tape of great titand other avian mobbing calls, they noted that “othersongbirds were lured inadvertently” (Zimmermann andCurio 1988). The following playback study documentsthe variety and behavior of species that are attracted toblack-capped chickadee (Parus atricapillus) mobbingcalls. Black-capped chickadees vocalize frequently, andare non-migratory and ubiquitous, so other avian specieson the study tract are likely to have had regular contactwith them. The chickadee calls would not be a novelsound to other birds.Playback studies testing interspecific communicationin a predator context have most often used avian alarmor distress calls and found mixed results. In responseto playbacks of their distress calls, swamp and songsparrows (Melospiza georgiana and M. melodia) appro-ached the speaker and called almost as frequently uponhearing each other’s distress calls as when they heardtheir own. They did not respond significantly to thedistress calls of the white-throated sparrow (Zonotrichiaalbicollis), nor did the white-throated sparrow respondto theirs (Stephanski and Falls 1972). Stephanski andFalls hypothesized that differences in call structure wereresponsible for the white-throated sparrows’ lack of res-ponse. Western grebes (Aechmophorus occidentalis)immediately flew from their nests when alarm calls ofForster’s terns (Sterna forsteri) were played (Nuech-terlein 1981). Nuechterlein suggested that the grebes’response to the tern alarm may have been due to learnedC.R. Hurd University of Wisconsin-Madison, Zoology Department Madison, Wisconsin 53706, USAassociation. California quail (Lophortyx californicus),scrub jays (Aphelocoma coerulescens), American robins(Turdus migratorius), western bluebirds (Sialia mexi-cana), western tanagers (Piranga ludoviciana), rufous-sided towhees, brown towhees (Pipilo fuscus), Oregonjuncos (Junco hyemalis oreganus), and house finches(Carpodacus mexicanus) flew from a field in which theywere foraging when house finch alarm calls were firstbroadcast, but the birds ceased responding to laterbroadcasts (Boudreau 1968). Though interspecific attraction to mobbing calls hasbeen casually observed in the field and is commonlyregarded as a widespread phenomenon, (Marler 1957;Klump and Shalter 1984), the few playback studiesdone showed that attraction to mobbing calls may notbe a general avian response but may be species or sitespecific. Curio (1971) found that playbacks of chaffinchmobbing calls attracted other chaffinches, blackbirds(Turdus merula), robins, great tits, and blue tits (Paruscaeruleus), but playbacks of pied and collaredflycatcher (Ficedula hypoleuca and F. albicollis) mob-bing calls attracted other species only in particularareas. Captive red-cheeked cordon bleus (Uraeginthusbengalus), blue-capped cordon bleus (U. cyanocephalus),and purple grenadiers (U. ianthinogaster) respondedsignificantly less to playbacks of each others’ predatorcalls than to playbacks of their own (Evans 1972). Mystudy is a census of the species of eastern North Ameri-can birds that are attracted to black-capped chickadeemobbing calls. These species may be important for anavian community’s successful defense against predators.In my experiment, I identified the species that wereattracted to broadcasts of the mobbing calls of black-capped chickadees. I recorded the species and numberof birds attracted, their duration of stay, and approachwithin 1 m of the playback speaker.MethodsEighteen sets of trials were conducted at the former nests of black-capped chickadees from 12 June to 6 July 1993. Chickadees hadabandoned these nests because of insect infestation, predation, orfledging of their young. Sets were conducted only at former chick-adee nests in order to increase the likelihood that birds of each areatested had had prior experience with black-capped chickadees.Sixteen of these sets were conducted on the Picnic Point study tractof the University of Wisconsin, one set at the University Arboretumand one set at a Madison residence. A