J. FieldOrnithol., 58(2):152-170 SONG DIALECTS AND NEIGHBORHOOD HABITATS IN THE INDIGOBIRDS VIDUA CHALYBEATA AND V. PURPURASCENS AT LOCHINVAR NATIONAL PARK, ZAMBIA ROBERT B. PAYNE Museumof Zoologyand Departmentof Biology The Universityof Michigan Ann Arbor, Michigan 48109 USA Abstract.--As part of a study of songdialects in the brood-parasiticAfrican indigobirds, habitatsof birds in different songdialect neighborhoodswere comparedin populationsof V. chalybeataand V. purpurascens.Univariate and multivariateanalyses of vegetationclasses, vegetationstructure, and resourceabundance at eachcall-site revealed no consistenthabitat differencesamong song neighborhoods of V. chalybeata.The sametechniques resolved sig- nificant differencesbetween the two indigobirdspecies. V. chalybeatahad three major song dialect repertoiresin the same area where V. purpurascensall sanga single songdialect repertoire.The lack of consistenthabitat differenceamong song dialect neighborhoods suggeststhat songneighborhoods in thesespecies are not explainedby differencesin the acousticproperties of songsin differenthabitats nor by geneticdifferentiation among local populationsadapted for different habitats.Supporting evidence of independenceincludes (1) the consistentdistribution of songneighborhoods over years of changinglocal habitats, (2) one instanceof a songneighborhood replacing another without a correspondingchange in local habitat, (3) the ongoingcultural evolutionof the fine detailsof all songsfrom year to yearin the absenceof any correspondingchange in habitat,(4) movementof birdsbetween songneighborhoods, and (5) a lack of congruenceamong song dialect areas of other bird speciesin the samehabitats. Observations of socialbehavior on the sameindividual indi- gobirdsprovides support for competitivesocial adaptation as the primary mechanismex- plaining the songsharing among neighbors. DIALECTOS EN HABITATS VECINOS DE VIDUAS (VIDUA CHALYBEATAY V. PURPURASCENS) EN EL PARQUE NACIONAL LOCHINVAR, DE ZAMBIA Sinopsis.--Comoparte dc un estudiosobrc dialcctos en avesparaslticas, sc cornpar6cl hfbitat de fireasvecinales de poblacionesde Viduachalybeata ¾ V. purpurascens,en donde habladiferencias en dialectos.Anflisis monovariable¾ multivariable del tipo de vegetaci6n, cstructurade csta, ¾ abundanciade recursosen cada lugar vecinal no revel6 difercncias para la especieV. chalybeata.E1 mismotipo de anflisis mostr6diferencias significativas al comparara ambas especies.V. chalybeatamostraba tres repertoriosde canciones,en las mismasfireas en dondeV. purpurascensmostraba un solodialecto de canciones.La ausencia dediferencias en el hfbitat de avesvecinas con dialcctos particulares, sugiere que la diferencia en el cantode gruposvecinales en estasespecies de viudas, no puede explicarsea basede diferenciasen las propiedadesac6sticas de los hfbitats, ni en las diferenciasgen&icas que puedahaber entre poblacioneslocales, como adaptaci6n al hfbitat particular que ocupan. La evidenciaque sugiercpatrones independientes incluye: 1) la distribuci•nconsistente de dialectosparticulares en fireasvecinas donde han ocurridocambios en el hfbitat a travis de los aftos,2) el casoparticular de un grupo con su propio dialectoque sustitu¾•a otro sin que ocurrierancambios en el hfbitat, 3) "evoluci•ncultural" de pequefios&talles en los cantosque ocurrendc afioen afio,sin que mediencambios en el hfbitat, 4) movimientode avesentre las vecindades,¾ 5) otras especiesen el mismohfbitat que no mantiencnla armonia de dialectos-cancionespor fireasvecinales. Observaciones sobre el comportamiento socialde individuosparticulares sugiere que son adaptacionessociales competitivas el me- canismoprincipal para explicarel porqu• avesvccinas fienden a compartircanclones par- ticulares. 152 Vol.58, •o. 2 SongDialects and Neighborhood Habitats [ 153 Microgeographicvariation in song characterizesa number of avian species.The featuresof songthat are restrictedto local populationsare referredto as song"dialects." Local songneighborhoods in which birds sharefeatures of their songthat differ from other suchlocal areasoccur in arian specieswith a diversityof life styles--residentand migratory birds, monogamousand polygamousbirds, and specieswith and without parental care of their young (Krebs and Kroodsma1980, Kroodsmaand Baylis 1982, Payne 1981a, 1983). The ecologicalcauses and conse- quencesof local songdialects have been linked with local behavioral adaptationsof birds to changingsocial contexts, to dispersalhistories of local populations,to effectson geneflow and populationdifferentiation, and to adaptationto local environmentalconditions, and may involve more than one of these (Adret-Hausberger1982, 1986; Baptista 1975; Craig and Jenkins 1982; Handford 1981; King 1972; Nottebohm1975; Payne 1978a,b, 1981a,b, 1983, 1985a,b; Shields1982; Wiens 1982). The questionof ecologicaladaptation has been developed more prom- inently in interspecificthan in intraspecificstudies, but habitat differ- encesappear to be associatedwith acousticdifferences both within and among speciesof birds (Bowman 1979, 1983; Gish and Morton 1981; Handford 1981; Heuwinkel 1982; Hunter and Krebs 1979; Jilka and Leisler 1974; King 1972; Marten and Marler 1977; Morton 1975; Not- tebohm 1975; Sorjonen 1983; Wasserman 1979; Wiley and Richards 1982). The hypothesisof ecologicaladaptation of songis of generalin- terest insofar as other behavior (Ewald 1980, Fretwell 1972, Holmes et al. 1979, Holyoak 1973, Wolf et al. 1976) and morphology(Fretwell 1972, James 1982, Leisler and Winkler 1985, Lederer 1984) may be correlatedwith local habitat conditionsboth within and among species. However, the studiesof within-speciessong variation have usuallybeen carriedout with unmarkedbirds in populationsof unknownhistory, and without concurrenttests on other possibledeterminants of local song differencesincluding the social interactionsand dispersalbiology. In additionto consideringpopulation biology of a species,it may be useful to compareother speciesin the same area to test whether they show a comparablemicrogeographic differentiation in their songs,in order to determinethe generalityof any habitat associationof local behavior. Song dialectscharacterize local populationsof severalspecies of Af- rican brood-parasiticfinches, including the Village Indigobird (Vidua chalybeata)and the Dusky Indigobird (V. purpurascens).The indigobirds are species-specificbrood parasitesof the firefinches(Lagonosticta spp.) (Nicolai 1964, Payne 1973). Their fosterspecies are similar in many of their habitat requirementsand as many as five speciesmay coexistin the samearea (Fry 1966, Payne 1973). The similarity in life stylesof the indigobirdspecies suggests a test of the idea that songdialects are asso- ciated with differences in local habitats. This association,if it exists, might be due to commonacoustic design features for soundtransmission in each habitat, or to geneticadaptation of populationsfor local condi- tions. In the secondcase, song differences among populationsmight be- 154] R.B. Payne J.Field Ornithol. Spring 1987 haviorallylimit the dispersalof birds beyondtheir songneighborhood or they might lessdirectly indicate markers of local demesthat havediffer- entiatedboth in behaviorand in geneticcharacteristics (Payne 1981a). As the two indigobirdsare similar in ecologyand in song structure, differing mainly in their fosterspecies and in the mimicry of their foster species'songs, one speciesprovides a test of the ecologicalsignificance of variation in the other. Two main questionswere askedin the presentstudy: (1) Are the song neighborhoodsassociated with different habitats?(2) Do the two species show the same microgeographicpattern of responseto the habitat? In addition,the independenceof songdialects and local habitatswas tested with a comparisonof changein songand habitat overseveral years, with observation of whether movements of marked birds were restricted to one habitat or songneighborhood, and with a cross-speciescomparison of songvariation in other songbirdsin the samearea. METHODS Indigobirdswere observedand their songsrecorded in a studyarea of about 40 km 2 at Lochinvar National Park, Zambia, 15ø57'S, 27ø15'E, from 1972 through 1979. A sample of singingmale V. chalybeatawas selectedfor observationof socialbehavior and individually marked with coloredleg bands (Payne and Payne 1977). Males generallyshared all songtypes in their repertoirewith their neighborsand nonewith remote malesin other songneighborhoods. A "neighborhood"is definedas the set of males that share the same songtypes, or songrepertoire dialect. The songtypes and songneighborhoods were usually obviousupon hear- ing the singingbirds in the field. A sampleof more than 30,000 songs of more than 100 V. chalybeataand more than 1000 songsof about 30 V. purpurascens(not all were color-marked)were recordedwith a Uher 4000-seriestape recorderand later were audiospectrographedwith a Kay Elemetrics"Vibralyzer" 7030A or a Princetonreal-time spectrumana- lyzer (PAR-4512) and photographedon 35-ram film. The results con- firmed the distinctivenessof songdialects in the local V. chalybeataand the uniformity of vocal repertoiresin the local V. purpurascerzs(Payne 1985a,b). The three songneighborhoods of V. chalybeatawere named cowpie,junction, and diptera (Fig. 1). The songneighborhoods of V. chalybeatachanged in area and in the number of birds with the songs over the years, with one songpopulation (junction) disappearing and another(diptera) expanding into thejunction area. Analysis of the habitats