The Condor95:588-595 0 The Cooper Ornithological Society 1993 GEOGRAPHIC VARIATION IN THE SONG OF THE RUFOUS-COLLARED SPARROW IN EASTERN ARGENTINA ’ PABLO L. TUBARO AND ENRIQUE T. SEGURA Laboratorio de Fisiologia de1Comportamiento, Instituto de Biologia y Medicina Experimental. Obligado2490. 1428 BuenosAires, Argentina PAUL HANDFORD Department of Zoology, Universityof WesternOntario, London, Ontario N6A 5B7, Canada Abstract. Variation in trill features of Rufous-collared Sparrow (Zonotrichia capensis) song is described in three sites located on the northeast coast of Buenos Aires Province, Argentina. There is a distinctive “talar” dialect in sites supportingnatural woodlands. This dialect is characterizedby slower trills with lower minimum frequenciesthan the one present in the open grassyfields (“steppe” dialect). Talar dialect is absent in a site where natural woodlands have been replaced by grassyfields and open man-made parks, suggestingthat the vocal tradition changedafter habitat modification. Detailed analysis reveals that talar and steppe dialects intergrade in a songcline, following the vegetational ecotone. This song cline has been stable in location and featuresduring the last decade, even though there were no geographicbarriers impairing population or cultural exchangebetween habitats. Key words: Rufous-collaredSparrow: Zonotrichia capensis;trill variation; dialect; song cline. INTRODUCTION thus giving rise to regional dialects (Nottebohm Bird song dialects, that is, particular types of 1969, 1975; Handford 1981, 1988; Lougheed et songsshared by birds inhabiting the same area, al. 1989). Rufous-collared Sparrow dialects have have been describedin several species(see Mun- been well studied in northwestern Argentina dinger 1982). Two of the most studied are the where there is a strong pattern of habitat varia- White-crowned Sparrow (Zonotrichia leuco- tion with longitude and altitude (Ring 1972; Not- phrys) (see Baker and Cunningham 1985, tebohm 1975; Handford and Nottebohm 1976; Kroodsma et al. 1985) and the Rufous-collared Handford 198 1, 1988; Handford and Lougheed Sparrow or Chingolo (2. capensis) (Nottebohm 1991). These studies have shown the existence 1969,1975; Nottebohm and Selander 1972; Ring of a relationship between trill dialect and vege- 1972; Handford and Nottebohm 1976; Hand- tation, and a high temporal stability in regional ford 198 1, 1988; Handford and Lougheed 199 1; dialect distribution during the last two decades. Lougheed and Handford 1992). In areaswith homogeneousvegetation trill fea- The song of this specieshas two parts: an in- tures seem to be relatively constant over great troduction and a final portion referred to as distances. For example, in the lowlands of Bue- “theme” and “trill,” respectively. The theme is nos Aires, Santa Fe and Cordoba Provinces, Not- usually composed of two to five whistled as- tebohm (1969, 1975) found a relatively homo- cending or descending notes. According to the geneousdialect (hereafter referred to as “steppe” number, shape and ordering of the notes, it is dialect), characterized by a trill interval of about possible to distinguish different themes. Within 60-70 msec. This area is also characterized by a an area, each male usually sings an individually homogeneousherbaceous steppe (the “Argentine distinctive theme. On the other hand, the main pampas,” Cabrera 1976). pattern of trill variation is among populations. Here, we describe the geographic pattern of In particular, trill interval (time between con- trill variation of the Rufous-collaredSparrow over secutive notes in the trill) is relatively constant a small geographic area located near the north- within an area, but it changesamong life zones, east coast of the Buenos Aires Province, Argen- tina. The original habitats present in this area included marsh, open woodland locally termed ’ ’ Received9 October1992. Accepted22 February “talar” for the dominant tree, “tala” (Celtis t&z), 1993. and steppe. However, at certain sites within this SONG VARIATION IN A SPARROW 589 area present-day vegetation differs from the orig- all the natural habitats are in a relatively good inal one, becausehuman activities have replaced state of conservation. the talar by grassyfields, gardensand parks. This Site B-Punta Indio: an area with some tourist situation opens the possibility for making song activity, where marked modifications in the orig- comparisons among sites where the original veg- inal vegetation have been made, mainly through etation still remains and those in which this veg- the elimination of the talar woodland and its etation has been replaced during the last few de- replacement by grassy fields, gardens and open cades. In particular, the aim of this study is: (1) parks. The size of the sampled area was about 3 to provide new evidence about the association km2, and comprises the marsh and steppe hab- between dialects and vegetation, (2) to study the itats as well as the place occupied in the past by shape and temporal stability of the dialect a well developed talar. boundaries, and (3) to assessthe possible effect Site C-Estancia Luis Chico: an area of about 1 of habitat change upon dialect distribution. km*, including only the talar and the steppehab- itat. This area has been partially altered because of the past exploitation of calcareous deposits, MATERIALS AND METHODS agricultural practices, and the introduction of The study area was located in the Partido of cattle. In this site the talar exists as a secondary Magdalena, on the northeast coastof Buenos Ai- growth and its physical structure is different from res Province, Argentina (Fig. 1). From the Rio that in Site A, mainly becauseof the small stature de la Plata inland, three different habitats can be and the dispersed distribution of trees. distinguished: Song sample. The songsof 897 adult individ- (1) Marsh: a seasonally flooding lowland and uals were recordedusing a UHER 4000 Report-L higher ground with grasscover, near the coast at a speed of 9.5 cm/set, and a directional car- of the Rio de la Plata. There are three dom- dioid Let 980 LEEA microphone. Wild 2. ca- inant communities of plants: Salicornia am- pensissingers are always males (King 1972), but bigua-Paspalum vaginatum; Scirpusolmery- the possibility that a small fraction of females Paspalum vaginatum-Distichlis spp.; and sometimes sing cannot be ruled out. Eight hun- Mentha pulegium-Pamphalea bupleurifolia. dred and forty-five individuals were recorded at (2) Talar: a xeromorphic woodland comprising Site A between October and January (59 in 1984- several tree species:Celtis tala (fam. Ulma- 1985; 24 in 1985-1986; 149 in 1986-1987; 215 ceae); Scutia buxzfilia (fam. Rhamnaceae); in 1987-1988; 72 in 1988-1989; 127 in 1989- Jodina rhombifolia (fam. Santalaceae) and 1990; and 199 during October 1991); 25 at Site Acacia caven (fam. Leguminosae), among B during January (16 in 1988-1989; and 9 in others. 1989-1990); and 27 at Site C, on 13 January (3) Steppe: an herbaceous open grassland, es- 1989. sentially without trees (with the exception of On each sonogram (made with a Kay Electric some planted rows of Eucalyptus sp., and a Sonagraph 7029-A, with the wide band setting few isolated C. tala. The main herbaceous and filtered to pass the 80-8,000 Hz frequency communities present in this area are: Stipa range) five trill featureswere measured: total du- charruana-Cynara cardunculus-Diodia das- ration, number of notes (NN), trill interval (TI) ycephala; S. charruana-Danthonia monte- (calculated as trill duration/[NN - l]), maxi- vidensis-Eryngium ebracteatum; Stipa pap- mum and minimum frequencies (FMAX and posa-Stenotaphrum secundatum-Distichlis FMIN, respectively). spp. Detailed descriptions of these commu- Statisticalanalysis. We made a two-way multi- nities can be found in Cabrera (1949) Parodi variate analysis of variance (MANOVA) using (1940), Vervoorst (1967) and Leon et al. three variables (IT, FMAX and FMIN), and the (1979). SYSTAT statistical package (Wilkinson 1987). In this analysis we included the 1987-l 988 song Within this area, we studied three sites (Fig. data from Site A, permitted by the completeness 1): of this sample. We also included the data from Site A-Estancia El Destino: an area of about 7 Site C, and the pooled data of 1988-1989 and km2. Part of this area is a private reserve, where 1989-1990 from Site B. In this case, the possi- 590 P. L. TUBARO, E. T. SEGURA AND P. HANDFORD BUENOS AIRES BUENOS AIRES PROVINCE BAHIA SAMBOROMBON FIGURE 1. Map showingthe locationof the studyarea: Site A (EstanciaEl Destino);Site B (Punta Indio); and Site C (EstanciaLuis Chico). bility of recording the same bird twice was neg- to the fact that talar and steppe songsdiffered at ligible for three reasons.First, the density of sing- Sites A and C, but not at Site B (Table 1). ers found at this site is high. Second, the song For convenience, we introduce the term “talar recordingswere made in different neighborhoods dialect” to refer to the slower trilled songs(higher for each period. Third, estimates of the disap- TI values) heard in talar, and use the term “steppe pearancerate for adult Rufous-collared Sparrows dialect” to refer to the faster TI songsheard on are high, ranging from 30 to 77.6% (Miller and steppe (Figs. 2, 4). At Site A, talar dialect also Miller 1968, Handford 1980). showed a lower FMIN than the steppe dialect Becauseof the small number of birds recorded (Fig. 3). Although there are clear songdifferences at marsh habitat in Sites A and B, we excluded in relation to the vegetation type, the pattern of these data from the formal analysis. However, song change is clinal and accompanied the en- they are plotted in Figures 2 and 3 for compar- vironmental ecotone. Figure 2 shows that this ison. TI cline at Site A has been stable during at least the last six years. Becauseof the small size and RESULTS uneven spatial distribution of the song samples Two-way MANOVA showed a significant effect taken during 1984-1985 and 1985-1986, they of site (Wilks’ Lambda = 0.607; F6,496= 23.40; are not presented,although they show essentially P < O.OOl), habitat (Wilks’ Lambda = 0.880; the same pattern of variation described above.