The Condor97z792-803 0 The Cooper OrnithologicalSociety 1995

GEOGRAPHIC, ECOLOGICAL AND SUBSPECIFIC VARIATION IN THE SONG OF THE RUFOUS-BROWED PEPPERSHRIKE (CYCLARHIS GUJANENSIS)’

PABLO L. TUBARO AND ENRIQUE T. SEGURA Laboratorio de Biologia de1Comportamiento, Institute de Biologia y Medicina Experimental, Obligado 2490. 1428 - BuenosAires, Argentina

Abstract. We describethe patternsof songvariation in the Rufous-browedPeppershrike (Cyclarhis gujanensis).Individual variation was estimatedusing a sampleof 659 songs belongingto 2 1 individuals.This analysisshowed that this speciesuses a repertoireof up to seven songtypes. Geographic, ecological, and subspecificpatterns of variation were estimatedusing four songsfrom eachof 93 birds recordedfrom Mexico to Argentina.On eachsonogram we measured10 temporal,frequency, and structuralfeatures of the song. Principal componentanalysis based on the correlationmatrix of thesedata showedthat subspeciessing similar songs. However, there were significant relationships between principal componentvalues and latitude,indicating that songsfrom equatorialareas are shorterin duration, have highermaximum frequencyand number of syllables,broader bandwidth and are lessrepetitive than thosefrom moretemperate areas. In addition,we classifiedthe recordingsites into threecategories according to the actualvegetation: open, mixed, and closed.A multivariateanalysis of varianceafter removing the effectof latitudeand altitude, showedthat habitat typesdiffer in songstructure. Songs from openand mixed areashave a narrowbandwidth, and a lower maximum, minimum and emphasizedfrequencies than thosefrom closedsites. We analyzedthese patterns according to the currentideas about soundpropagation in naturalenvironments and the geographicalpattern of body sizevari- ation in the Rufous-browedPeppershrike. Key words: Rufous-browedPeppershrihz; Cyclarhis gujanensis; song; subspecies; latitude: altitude; habitat; reverberationhypothesis; Bergmann s’ rule.

INTRODUCTION the attenuation of different frequencies (Morton The analysis of bird-song features and their re- 1975, Marten and Mailer 1977, Marten et al. lationship to habitat structure has been a subject 1977). These studiesreported the existenceof an of researchsince the pioneering studies of Chap- “acoustic window” near the forest ground which puis (197 1) and Morton (1975). Those studies favors the use of low frequencies for long-range showedthe existenceof songdifferences between communication in closedhabitats. However, this bird communities living in tropical forests and observation does not explain why speciesliving open fields. In particular, Morton (1975) found one or two meters above the ground or in open that the frequencies used by tropical forest spe- areasdo not use still lower frequencies,since they cies are lower than those from open tropical ar- presumably would propagate even better. Ryan eas. This relationship remained valid even when and Brenowitz (1985) suggestedthat differences differences in body size and phylogenetic effects in spectral distribution of ambient noise could were accounted for (Ryan and Brenowitz 1985). explain such a difference. In addition, Wiley and More recently, Wiley (199 1) found that, on av- Richards (1982) stressedthe effectsof reverber- erage, the maximum frequency of temperate for- ation rather than differencesin frequency atten- est songsis lower than those of marsh and grass- uation among habitats as the main selective fac- land. However, the causes of this relationship tor in songdesign. According to this view (hence- are not clear. forth referred to as the “reverberation hypoth- Early attempts to explain the relationship be- esis”), in addition to frequency, the temporal tween frequency of songsand habitat focusedon structure of the song is important for long-range communication. Slowly modulated signals are favored in forests,because they avoid the acous- tic degradation generated by the accumulation I Received3 January1995. Accepted1 May 1995. of ethos. In open fields, the main sourceof acous-

WQI SONG VARIATION IN THE RUFOUS-BROWED PEPPERSHRIKE 793 tic degradation is random amplitude fluctuation and eCOlOgiCa faCtOrS may influence song struc- produced by moving cells of air with different ture. temperature and humidity. This favors signals The song of the Rufous-browed Peppershrike with high rates of repetition (Wiley and Richards has not been describedusing representative sam- 1978, Richards and Wiley 1980). ples of sonograms and cuantitative measure- The predominance of rapidly modulated ments of frequency and temporal variables. This sounds in songs from grass and edge habitats, specieshas a repertoire of two songtypes: a very and the presenceof pure tone, slowly modulated infrequent, slow seriesof four to eight descending songsin forest, was describedby Morton (1975). notes (which is attributed to the female), and a A recent study of the vocalizations from bird musical whistled song, with multiple ascending communities of eastern North America also and descending modulated notes (Skutch 1967). showed that temporal properties of song were We considered the later as the primary song of strongly associatedto habitat (Wiley 199 1). Spe- the species and we will refer exclusively to it cifically, birds of forest avoided the use of notes hereafter. with short repetition periods, as predicted by the reverberation hypothesis. METHODS Another line of research on song design con- Recordings used in this study were derived from cerns the study of single speciesliving in a di- a variety of sources;recording localities and oth- versity of habitats. In spite of the limited gen- er details are provided in Appendix 1. The sam- erality of this approach, it has the advantage of ple includes songsof 93 individuals from within reducing the confounding effects of phylogeny the ranges of seven subspecies(sample sizes in- and morphology in songcomparisons. Studies of dicated in parentheses):C. g. flaviventris (5), ni- the White-throated Sparrow (Zonotrichia albi- caraguae (16) subflavescens(lo), ochrocephala collis, Wasserman 1979, Waas 1988), the Sum- (32), gujanensis (12), pawus (8), and saturatus mer Tanager (Piranga rubra, Shy 1983), the (10). These samplescover almost the entire range Northern Cardinal (Cardinalis cardinalis, An- of latitudes and altitudes over which this species derson and Conner 1985), and the Great Tit is found (Fig. 1). Subspecific identity was as- (Parus major, Hunter and Krebs 1979) indicate signed according to the geographic location of the use of lower frequencies and narrower band- the songrecording and the following bibliograph- width in forested than in more open habitats. ic sources: Chapman (19 17, 1926), Griscom However, the Rufous-collared Sparrow (Zono- (1932), Hellmayr (1935), Dickey and Van Ros- trichia cape&s) appears to show the opposite sem (1938), Pinto (1944) Phelps and Phelps pattern, with higher frequency and broader band- (1963), Olrog (1979), and Howard and Moore width associated with more closed and mesic (199 1). Environmental information (altitude and environments (Nottebohm 1975, Handford and habitat type) was derived from the data sheets Lougheed 199 1). This speciesalso avoids the use accompanying the recordings. Latitude was in- of rapid trills in forested areas, thus conforming ferred in missing cases,using the geographicco- to the predictions ofthe reverberation hypothesis ordinates of the recordingsite. Habitat types were (Nottebohm 1975, Handford 1988, Handfordand classifiedinto three categories:closed (including Lougheed 199 1, Tubaro et al. 1993). tropical humid forestand montane forest),mixed This diversity of phenomena indicates the need (including coniferous forest, mixed forest and de- for other comparative studies. In this paper we ciduous forest), and open (arid scrub, gardens, present an analysis of the pattern of song vari- and savannas). ation in the Rufous-browed Peppershrike (Cy- On each sonogram (made with a Proaudio clarhisgujanensis). This specieslives in a variety Spectrum 16 Sound Blaster [Media Vision] and of habitats ranging from mesic forest to xero- the ADDA 16 software [LIS 19921)we measured morphic woodlands and arid savannas,and from the following variables (see Fig. 2): song length the sealevel to 3,500 m in the Andes Mountains. (SOLEN), note length (NOLEN), intemote in- It also shows a high degree of polytypism, with terval (INI), maximum and minimum frequen- 2 1 subspeciesdescribed in its range from eastern cies (MAX and MIN, respectively), bandwidth Mexico to central Argentina (Howard and Moore (BAND = MAX-MIN), emphasized frequency 199 1). This provides the possibility for clarifying (frequency with the higher amplitude in the song, the extent to which phylogenetic, geographical, ENF), number of notes (NN), number of sylla- 194 PABLO L. TUBARO AND ENRIQUE T. SEGUR4

pat-w.6

gujanensis

subflavescens

Y safuratus

l 1

0 2

FIGURE 1. Locationof songsamples, as well as the approximatedistribution of the subspeciesconsidered. The sizeof the filled circlesindicates the numberof birdsrecorded in eachsite.

bles (NS), and a “repetition index” (RI). The RI 15-l 00). Details of the provenance of these re- is the mean number of times a syllable type is cordings are shown in Appendix 2. Song types consecutively repeated in a single song. We de- were defined according to the shape and order fine notes and syllables according to Tubaro of syllables. Since we found that the Rufous- (1992). browed Peppershrike has a repertoire of several Individual variation was studied using 659 song types (mean = 1.95, range = l-7), we used sonogramsbelonging to 2 1 subjectswith record- a “bootstrap” approach in the study of geograph- ed samples greater than 15 songseach (range = ical variation in song. We randomly chose one SONG VARIATION IN THE RUFOUS-BROWED PEPPERSHRIKE 195

SOLEN

, SYLLABLE 1 NOLEN MAX

MIN NOTE

1 SEC.

FIGURE 2. Sonogramof a songof Cychrhis gujunensis showingsome of the variablesmeasured. For acronyms see Methods. song from each individual in the original sample analysis showed that PC1 varies positively with (n = 93 individuals) and ran the multivariate BAND, MAX, NS, and negatively with SOLEN. analyses described in the subsequentparagraph. PC2 corresponds to an axis of increasing SO- To assessthe robustness of our results we re- LEN, NN, and RI. Finally, PC3 correspondsto peated this procedure four times, including dif- an axis of decreasingENF, MAX, MIN and INI. ferent song types or different renditions of the Taken together,these three axis accountfor 69.5% same type depending on the repertoire size of of the total variance in the original set of data. each individual. Subspecificvariation. Six of seven subspecies For each bootstrap replicate, we performed a included in the study sing very similar songs,as Principal Component Analysis (PCA). This pro- suggestedby the high degree of overlap in the cedure summarizes major trends of a data set 95% confidenceellipses depicted in Figure 3. Only and reducesthe ten variables measured on songs C. g. ochrocephala(the race living along the At- to a small number of independent variables. Then, lantic coast of South America) tended to score we regressedthe principal component scoresof lower in PC1 and higher in PC2, indicating songs all individuals on log-transformed values of both with relatively narrow bandwidth, lower maxi- latitude and altitude. We also compared the re- mum frequency and highly repetitive structure. siduals of variation (i.e., partitioning out the ef- Since thesedifferences are not absolute (i.e., there fect of altitude and latitude) among habitats us- are still wide overlaps in both PC1 and PC2, as ing a multivariate analysis of variance (MAN- well as in PC3 values among all subspecies)we OVA). proceeded with geographicand ecological anal- Although there are no morphological mea- yses of song variation, pooling all subspecific surements of the recorded birds included in this samples. study, geographicvariation in body size was es- Latitude and altitude. Multiple regression of timated using the wing chord and tail length of the 65 birds in which information about the en- 90 skins deposited in the Museo Argentino de vironmental variables was complete shows that Ciencias Naturales Bernardino Rivadavia. In ad- a significant amount of variation in PC1 (R* = dition, we found some measures published in: 0.23,P<0.003)andPC2(RZ=0.25,P<0.0001), Chapman (19 17), Gyldenstolpe (1945), and Wet- but not in PC3 (R* = 0.035, P > 0.3), was ex- more et al. (1984). Unfortunately, most of these plained by both altitude and latitude. In both authors reported only means and their data cases,latitude was the only variable which con- therefore were deleted from the statistical anal- tributed significantly to variation in PC 1 (partial ysis. correlation = -0.28, te3 = -2.32, P = 0.0238) and PC2 (partial correlation = 0.49, t,, = 4.44, RESULTS P < 0.0001). These analyses indicated that, at Since the results of the analysis of the four sets higher latitudes, songs are longer, more repeti- of data were similar, we only present details of tive, have narrow bandwidth, lower maximum one set (Tables 1,2, and 3). Principal component frequency, and a higher number of notes than

SONG VARIATION IN THE RUFOUS-BROWED PEPPERSHRIKE 791

3.5

ochmcephala 2.5

g 1.5 > s 8 0.5 6 t g -0.5 a flaviventris -1.5

-2.5 ' -3 -2 -1 0 1 2 3 PC1 (34.70% var.) FIGURE 3. 95% confidenceellipses around subspeciesmeans of songcharacters PC1 and PC2. PC 1 correspond to an axis of increasing BAND, MAX, NS and decreasingSOLEN. PC2 correspondto an axis of increasing SOLEN, NN and RI. For acronyms see Methods. those recorded near the equator (Fig. 4). In only intemote intervals, narrow bandwidth, and low- one of four sets of data was there a significant er maximum, minimum and emphasized fre- relationship between principal components and quencies than those from closed sites. altitude, with the songsof the highlands having Bergmanns’ Rule. Body size, as estimated by wider bandwidth, shorter notes and longer in- wing chord and tail length, showed a positive temote interval. trend with latitude (R* = 0.289, P < 0.000 1, and Habitat. The MANOVAs on the residuals of R2 = 0.537, P < 0.0001, respectively). Thus, variation in principal components values (after Cyclarhis gujanensisseems to conform to Berg- removing the effects of altitude and latitude) mann’s Rule (Fig. 5). Although most of the em- showeda significant or marginally significant in- pirical evidence supporting Bergmann’s Rule fluence of habitat on song structure (in three of comes from temperate regions, at least two other four “bootstraps”). These analysesindicated that neotropical species have shown such a pattern the songsfrom open and mixed siteshave shorter of variation: the Carbonated Flower-Piercer (Di-

TABLE 2. Correlation (Pearson)matrix among song variables. For acronyms see Methods.

SOLEN NOLEN INI MAX MIN BAND ENF NN NS RI

SOLEN 1.oo NOLEN 0.22 1.00 IN1 0.27 0.38 1.00 MAX -0.09 -0.38 -0.03 1.00 MIN -0.04 0.08 0.11 0.27 1.00 BAND -0.08 -0.43 -0.07 0.81 -0.30 1.oo ENF 0.16 -0.24 0.07 0.55 0.25 0.40 1.00 NN 0.52 -0.64 -0.25 0.17 -0.15 0.24 0.31 1.oo NS 0.17 -0.57 -0.39 0.31 -0.27 0.46 0.29 0.69 1.00 RI 0.35 0.41 0.17 -0.34 0.10 -0.40 -0.09 -0.04 -0.25 1.oo 798 PABLO L. TUBARO AND ENRIQUE T. SEGURA

TABLE 3. Factor loadings from the principal com- not clear yet, becausethe lower the frequency the ponent analysis carried out on the song variables. These less it attenuates with distance when broadcast results are derived from only a single bootstrap. For at a height greater than one meter above the acronyms see Methods. ground (Morton 1975, Marten and Marler 1977,

COIlIpOU.?llt Marten et al. 1977). 1CdiIlgS PC1 PC2 PC3 In our study, the presenceof higher frequencies SOLEN 0.002 0.848 -0.358 in the songsfrom tropical areas might have been NOLEN -0.794 0.043 -0.255 expectedsince: (a) body size in the Rufous-browed IN1 -0.369 0.060 -0.589 Peppershrike increases with latitude, thus con- MAX 0.693 -0.370 -0.516 forming to the Bergmann’s rule, and (b) there is MIN -0.226 -0.156 -0.591 a negative relationship between body size and BAND 0.773 -0.253 -0.173 ENF 0.525 0.032 -0.635 frequencies used in the song (Bowman 1979, NN 0.671 0.665 0.060 1983; Wallschlager 1980; Ryan and Brenowitz NS 0.792 0.334 0.212 1985). We therefore expect birds from tropical RI -0.497 0.516 -0.211 areas to use higher frequencies in their songs. % variance 34.699 17.985 16.818 However, this explanation must be taken with caution because the allometric relationship be- tween frequency of the song and body size may glossa carbonaria, Graves 199 l), and the Yel- not apply for some speciesor frequency features. low-billed Cacique (Amblycercus holosericeus, For example, Handford and Lougheed (1991) Kratter 1993). found that syrinx size is not related to body size, suggestingthe absence of a physical constraint DISCUSSION on frequencies used in the song. In addition, in This study showsthe existence of a relationship Geospizadi$icilis (Bowman 1979, 1983) and Pi- between song structure and geographic and en- ranga rubra (Shy 1983), larger individuals have vironmental variables such as latitude, and hab- song with higher frequencies. Unfortunately, we itat. In particular, songs from equatorial areas lack data to test this possibility in the Rufous- have broader bandwidth, with higher maximum browed Peppershrike. frequencies, and are shorter and less repetitive Superficially,latitudinal differencesin body size than those from more temperate latitudes. may seem to explain why in closedhabitats, usu- The presenceof higher frequencies in the Ru- ally occurring near the equator where birds are fous-browed Peppershrike songsfrom closedar- smaller, songshave both higher maximum and eas contrasts with most previous work on other emphasized frequencies than in open habitats, species. For instance, the occurrence of wider usually occurring at higher latitudes where birds band sounds with higher maximum frequencies are bigger. We have attempted to remove the is characteristic of open habitats from tropical effect of latitude and altitude from our analyses and temperate areas (Chappuis 1971, Morton and, thus, the presence of higher frequencies in 1975, Wiley 1991). These studies also showed closed habitats would appear to be due to some that, in general, closed habitats have narrow other factor. However, we do not know if there bandwidth sounds, with lower frequencies, thus are body size differencesamong habitats that are conforming to the findings for the northern Car- unrelated to latitude. For example, natural se- dinal (Anderson and Conner 1985), the Summer lection might favor smaller birds in densely veg- Tanager (Shy 1983) the White-throated Sparrow etated areas compared to more open habitats. (Wasserman 1979, Waas 1988), and the Great This association would not have been removed Tit (Parus major, Hunter and Krebs 1979). In by the regression analysis of song features on contrast, but similar to the Rufous-browed Pep- latitude, and thus the effect of body size may still pershrike, the songsof the Rufous-collared Spar- be confounding our attempts to examine the re- row are up to 3 kHz higher near the equator lationship between habitat and song structure. (Nottebohm 1975) and the use of higher maxi- More recent studies about the effect of ecolog- mum frequencies is associated with mesic,. ical factors on song design have focusedon tem- densely vegetated habitats (Handford and poral aspectsof the signal (Wiley and Richards Lougheed 199 1). Acoustical reasons for the use 1978, Richards and Wiley 1980, Wiley 1991). of different frequencies in different habitats are According to the reverberation hypothesis, we SONG VARIATION IN THE RUFOUS-BROWED PEPPERSHRIKE 799

3r 8 2 O 0 0 0 1 s" 0 0 Oo 00 ----c go oo" ---we 1 O 00 8 -1 I 8 :0

-2 0

-0 5 10 15 20 25 LATITUDE

0 0

0 8 0

0

-._ -I 0 5 10 15 20 25 30 35 40 LATITUDE FIGURE 4. Regressionof PC1 scores(top), and PC2 scores(bottom) on latitude.For acronymssee Methods. could expectlonger silencegaps among songnotes islands, tend to have simpler and more variable in densely vegetated habitats, as a way to avoid songs (see also Lack and Southern [ 19491). degradation caused by ethos. In fact, we found Thielcke (1973) developed essentially the same slightly longer intemote intervals in closed areas idea using the term “loss of contrast” for refer- than in more open ones. ring to the loss of species-specificdifferences in Regarding the relationship between variability song in the absenceof coexisting related species. of song syntax and complexity of the acoustic The importance of the “sound environment” in environment, Marler (1952) suggestedthat the shaping the species’ song has been further de- song of a local population of a species should veloped and partly testedin recent years. Nelson differ significantly from that of other species (1988, 1989) demonstrated that both variability sharing the same local habitat. Thus, birds living and a feature’s central tendency relative to other in regions with impoverished avifaunas, such as speciesin the local acousticenvironment are im- 800 PABLO L. TUBARO AND ENRIQUE T. SEGURA

94

n 82 8 5 76

64' 0 5 10 15 20 25 30 35 40 LATITUDE

84

48' 0 5 10 15 20 25 30 35 40 LATITUDE FIGURE 5. Regressionof wing chord and tail length (both in millimeters) on latitude. Small circles indicate individual values. Large circlescorrespond to data publishedelsewhere, and they were not included in statistical analysis. portant in species-songrecognition. According prediction, there is no trend in song variability to thesehypotheses and considering the existence among subspecies,(table l), in spite of differ- of a higher diversity of birds in the tropical forest ences in latitude (see Fig. 1). In addition, the than in more temperate or open areas,we predict songsC. g. ochrocephalaare clearly more repet- the occurrenceof simpler (i.e., with less number itive than those of the other subspeciesliving in of notes and syllables) and more variable songs more tropical or forested environments (like C. (i.e., with less repetitive structure and/or higher g. gujanensis or C. g. parvus). Songs of ochro- coefficient of variation in their features) in the cephala, and to a less extent in nicaraguae and latter than in the former habitat. Contrary to our saturatus, are composed of notes grouped into SONG VARIATION IN THE RUFOUS-BROWED PEPPERSHRIKE 801 syllables. These, in turn, are repeated consecu- of the Rufous-collared Sparrow, Zonotrichia ca- tively. It is improbable that variation in body .oensis.with respect to habitat, trill dialects and size among subspeciescould explain these dif- body size. Condor 93:644-658: HELLMAYR.C. E. 1935. Cataloaue of birds of the ferencesin song syntax. Rather subspecificvari- Americasand the adjacentisl&ds. Field Mus. Natl. ation in syntax is probably the result of phylo- Hist. Zoological Series 13. genetic, historical, learning, and ecological phe- HOWARD, R, AND A. MOORE. 1991. A complete nomena. checklistof the birds of the world. Academic Press, London and San Diego. ACKNOWLEDGMENTS HUNTER.M. L.. ANDJ. R. Knnns. 1979. Geoaraohical_ . variation in the songof the Great Tit, Parus major, We thank A. Lemoine, G. Lichtenstein, S. Lougheed, in relation to ecologicalfactors. J. Anim. Ecol. 48: J. C. Reboreda, R. Fraga, and P. Handford for their 759-785. comments on several versions of the manuscript, and Ka~n-n~, A. W. 1993. Geographic variation in the J. Navas for making available the collection of the Yellow-billed Cacique, Amblycercusholosericeus, Museo Argentino de CienciasNaturales. We alsothank a partial bamboo specialist.Condor 95:641-651. the recordist mentioned in Appendix 1 and 2, the Na- LACK,D., ANDH. N. SOUTHERN.1949. Birds on Ten- tional Sound Archive Wildlife Section, the Bioacoustic erife. Ibis 91:607-626. Archives and Library, the Florida Museum of Natural LIS. 1992. Laboratorio de InvestigacionesSensori- History, and the Library of Natural Sounds, Cornell ales. Informe XXV. 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ican highland birds. Publ. Nuttall. Omithol. Club Falls, Misiones Province, AR, LNS 34040,23754 (T. No 7. Cambridge, MA. Parker), Itambezhino, Rio Grande do Sul, BR, LNS THIELCKE,G. 1973. On the origin and divergenceof 20136,20138 (W. Belton), Tenente Portela, Rio Gran- learned signals(songs) in isolated_oonulations. _ Ibis de do Sul; BR; LNS 19852 (w. Belton), Canela. Rio 115:511-516. - ’ Grande do Sul; BR, LNS 20 137 (W. Belt&), Sao Fran- TUBARO,P. L. 1992. Song repertoires of the White- cisco de Assis. Rio Grande do Sul. BR: LNS 22108. browed Blackbird. Wilson Bull. 104:345-352. 22123, 22127; 32203, 32223 (T. Parker), Itatiaia Na- TULIARO,P. L., E. T. SEGURA,AND P. HANDFORD.1993. tional Park, Rio de Janeiro, BR, LNS 20140 (W. Bel- Geographic variation in the song of the Rufous- ton) Itatiba do Sul, Rio Grande do Sul, BR, LNS 20 139 collared Sparrow (Zonotrichiu cupensis)in eastern (W. Belton), Lagoa do Jacare,Rio Grande do Sul, BR, Argentina. Condor 95:588-595. LNS 32183, 32185 (T. Parker), Tijuca Forest, Rio de WAAS, J. R. 1988. Song pitch-habitat relationships Janeiro, BR, NSA 4083 (D. W. Snow), BoraceiaForest, in White-throated Sparrow: cracksin the acoustic San Pablo, BR, LNS 39090,39092 (T. Parker), Itatiaia windows? Can. J. Zool. 66:2578-258 1. National Park, Minas Gerais, BR, LNS 10962 (R. WALL~CHL.&GER,D. 1980. Correlation of song fre- Ward), Santa Teresa, Espiritu Santo, BR. quency and body weight in passerine birds. Ex- C. g. gujunensis:LNS 48713 (M. Cohn-Haft), Ma- perientia 36:4 12. naus, Amazonas, BR, LNS 32419, 32441 (R. Bierre- WASSERMAN,F. E. 1979. The relationship between gaard), Manaus, Amazonas, BR, ARA 7 (W. B. Mc- habitat and song in the White-throated Sparrow. Gillivray), Saul, GU, NSA 8983 (V. J. Mees-Balchin), Condor 8 1:424-426. Rappel Savanne,SU; NSA 29370 (V. J. Mees-Balchin), WETMORE,A., R. F. PASQUIER,AND S. L. OLSON. 1984. Dadanawa Ranch, Rupumuni, SU; LNS 455 18,45528, The birds of the Renublic of Panama. Part 4- 45531, 45537 (T. Parker), El Dorado, Bolivar, VE, Passeriformes:Hirundinidae (swallows) to Frin- LNS 30478 (T. Parker), Santa Elena, Bolivar, VE; LNS gillidae (finches). Smithsonian Institution Press, 38970 (T. Parker), Pando, BO. Washington, DC. G. g. purvus:ARA 7 (J. C. Hardy), Caracas,VE; LNS WILEY, R. H. 1991. Associationsof song properties 47830 (M. Isler), Miranda, VE, LNS 40360 (P. Coop- with habitats for territorial oscine birds of eastern mans), Aragua, VE, LNS 10948, 10950, 10956 (P. North America. Am. Nat. 138:973-993. Schwartz), Petare, Caracas,VE; LNS 10952,10953 (P. WILEY, R. H., AND D. G. RICHARDS. 1978. Physical Schwartz), Los Palos Grandes, Caracas.VE. constraintson acousticcommunication in the at- C. g. s&rutus: LNS 28761 (A. B. van den Berg), mosphere. Implications for the evolution of ani- Huanuco. PE: LNS 17389. 17392 (T. Parker). Cum- mal vocalizations. Behav. Ecol. Sociobiol. 3:69- pang, La’Libertad, PE, NSA 25528 (N. Krab’be), Pa- 94. chachupar, Huanuco, PE; LNS 18023 (J. P. O’Neill), Wnsv, R. H., AND D. G. RICHARDS. 1982. Adapta- Bagua,Amazonas, PE, LNS 2 1620 (T. Parker), Huan- tions for acousticcommunication in birds: sound cabamba,Piura, PE, LNS 294 12 (T. Parker), Huanuco, transmissionand signal detection, p. 13l-l 8 1. In PE; LNS 26918 (M. Isler & P. Isler), Huanuco, PE; D. E. Kroodsma and E. H. Miller [eds.], Acoustic NSA 25525 (N. Krabbe), Carpish mountains, Huan- communication in birds, Vol. 1. Academic Press, uco, PE. BAL 2 (T. Parker), Huanuco, Cordillera Div- New York. isoria, PE. C. g. subjhvescens:LNS 10966, 10967 (E. S. Morton APPENDIX 1 & L. B. Morton), Volcan de Chiriqui, PA, LNS 10959 (L. I. Davis & D. Davis), Cerro Punta, PA, LNS 10968 Sourceof songs,grouped by subspecies.Abbreviations (E. S. Morton), Volcan de Chiriqui, PA; LNS 28245 are as follows: LNS: Library of Natural Sounds,Cornell (A. B. van den Berg), Monteverde, Puntarenas, CR, Laboratory; NSA: National Sound Archive Wildlife BAL 6, 7 (G. Stiles), Valle Central, CR, BAL 22 (J. Section; BAL: BioacousticArchives and Library, Flor- Arvin), Tupuntec National Wildlife Refuge, Heredia ida Museum of Natural History; ARA 7: Songsof the Province, CR, LNS 37750 (D. Minia), Tapanti Wildlife vireos and their allies. Cassette.compiled and edited Reserve, Cartago, CR, NSA 18734 (R. Ranft), Volcan bv J. C. Barlow and J. W. Hardv: PLT: Pablo Luis Barra, CR. Tubaro personalcollection; AR: Argentina; BR: Brazil; C. g. nicuruguue:LNS 10971, 20376 (W. A. Thur- CO: Colombia; VE: Venezuela; PE: Peru; SU: Suri- ber), Parque Deneinger, La Libertad, SA, LNS 10969 name; GU: Guyana; PA: Panama; NI: Nicaragua;SA: (W. A. Thurber), Chanmico, La Libertad, SA; LNS El Salvador;CR: CostaRica; ME: Mexico. The number 20346 (W. A. Thurber), Cerro Verde, Santa Ana, SA, following recording’s source identify the specimen LNS 10960 (L. I. Davis & D. Davis), Esteli, NI; BAL studied accordingto the respectivecatalog. Recordist’ 10, 11, 12, 13, 14, 15 (T. Webber), Parque National name in parenthesis. Lagunas de Montebello, Chiapas, ME; BAL 1 (J. W. C. g. o&roce&zZu: PLT 158, 159, 160, 161 (P. L. Hardy), Pueblo Nuevo, Chiapas, ME; BAL 20 (G. Las- Tubaro), Estancia El Destino, Partido of Magdalena, ley), Paval, Chiapas, ME; LNS 10942 (L. I. Davis), Buenos Aires Province, AR, PLT 156, 157 (P. L. Tu- Puente Central, Chiapas,ME; LNS 10943(L. I. Davis), baro), Atalaya, Partido of Magdalena, Buenos Aires Tuxtla Gutierrez, Chiapas, ME, LNS 10944 (L. I. Da- Province, AR, PLT 170,17 1,172 (P. L. Tubaro), Delta vis), Comitan, Chiapas, ME. ofParana River, BuenosAires Province, AR, PLT 162, C. a. fluviventris:BAL 4 (J. W. Hardv). Gomez Far- 163 (P. L. Tubaro), Campo Rico Island, SantaFe Prov- ias, Tamaulipas, ME; LNS-45648, 45649, 45671 (C. ince, AR. PLT 165 (P. L. Tubaro), El Cenito Island, D. Duncan), Tamaulipas, ME, LNS 10961 (L. I. Davis Chaco Province, AR, LNS 34060 (T. Parker), Iguazu & D. Davis), Jacala, Hidalgo, ME. SONG VARIATION IN THE RUFOUS-BROWED PEPPERSHRIKE 803

APPENDIX 2 Grande do Sul, BR, LNS 20 137 (W. Belton), Sao Fran- cisco de Assis, Rio Grande do Sul, BR, LNS 20138 Source of songsused in the analysis of the individual (W. Belton), Turvo Forest Reserve, Rio Grande do Sul, variation. Abbreviations are as in Appendix 1. BR, LNS 20346 (W. Thurber), Cerro Verde, SantaAna, LNS 10942 (L. I. Davis), Chiapas, ME; LNS 10948, SA, LNS 20376 (W. Thurber), Parque Deneinger, La 10956 (P. Schwartz), Petare, Caracas,VE; LNS 10961 Libertad, SA, LNS 23092 (R. Waide), Cozumel Island, (L. I. Davis and D. Davis), Hidalgo, ME; LNS 10962 Quintana Roo, ME, LNS 22127 (T. Parker), Itatiaia (R. Ward), Espirito Santo, BR, LNS 10966 (E. S. Mor- National Park, Rio de Janeiro, BR, LNS 21620 (T. ton and L. B. Morton), Volcan de Chiriqui, PA, LNS Parker), Huancabamba, Piura, PE; LNS 26918 (M. Is- 10968 (E. S. Morton), Volcan de Chiriqui, PA, LNS ler and P. Isler), Huanuco, PE; LNS 487 13 (M. Cohn- 10971 (W. A. Thurber), Parque Deneinger, La Liber- Halt), Manaus Reserve, Amazonas, BR, LNS 45518, tad, SA, LNS 17392 (T. Parker), Cumpang, La Lib- 45537 (T. Parker), El Dorado, Bolivar, VE. ertad, PE, LNS 19852 (W. Belton), Moro Pelado, Rio