The Condor 90:44-50 0 The Cooper Ornithological Society 1988

THE FORM AND FUNCTION OF SONG IN FEMALE SONG SPARROWS

PETER ARCESE~ Department of Zoology, Universityof , Vancouver,British Columbia V6T 2A9,

PHILIP KRAFT STODDARD Department of Psychology,University of Washington,Seattle, WA 98195

SARA M. MIEBERT Department of Zoologv Universityof Washington,Seattle, WA 98195

Abstract. We report on the occurrenceand context of female song in the color-marked SongSparrow ( melodia)population resident on Mandarte Island, British Colum- bia. Sonogramsof three females showed that the structureof female song varied, but was usually less complex than that of males. At least one female’s song was within the male range of complexity and could have been mistaken for a male songhad the sex of the been unknown. Another female sangat least two distinct song types. Further, the songsof females recorded on Mandarte were similar to those recorded elsewherefrom wild females and from captive females implanted with testosterone.Overall, singingby females on Man- darte was rare; only 12 of approximately 140 females were heard singingduring 267 female- years of intensive observation. With one exception, female song was heard only from late February to mid-April, the period just prior to nest building when territory turnover and settlementby yearlingsis most common. Most females (83%) sangduring territorial conflicts betweenfemale intruders and female territory owners. Female songwas more common when population density was high, average breeding successwas depressed, and variation in breeding successwas increased.We suggestthat songresults from elevated levels of testos- teronein femalesthat are engagedin intrasexualaggression, and we discusssome implications of female song for hypothesesof song learning. Key words: Melospiza melodia; Song Sparrow;territoriality: testosterone;female aggres- sion; songlearning.

INTRODUCTION 1975, Richison 1983). Nice (1943) suggestedthat Nice (1943) reviewed the occurrence of female female passerinesfell into two groups,depending bird song and speculatedon its evolution. After on whether song was a common or exceptional a considerable gap, renewed interest in the song aspect of their behavior. She placed Song Spar- of female has concerned its role in court- rows in the latter group. Nice (1943) speculated ship and maintenance of the pair bond, family further that the female Song Sparrows she ob- unit, and territory (Beletsky 1982, 1983a, 1983b; served singing were unusually aggressiveindi- Richison 1983, 1986). In this study, we focused viduals and had abnormally high levels of an- on singing female Song Sparrows (Melospiza drogens. Her suggestion seems reasonable melodia) in a color-marked island population. because,in some speciesin which females rarely We discussthe context of female song, present or never sing, singing can be induced by im- sonograms from six females, and compare our planting testosterone (references in Nice 1943, observations with those of Nice (1943). Finally, Nottebohm 1975). However, Wingfield (1984a, we speculate on the function of female song in 1984b) has shown that in wild Song Sparrows, Song Sparrows. circulating levels of testosteronein females at the Except in a few species,singing by female pas- time of territory establishment and just prior to serinesis rare (reviews in Nice 1943, Nottebohm nest building are normally almost as high as those recorded in males at the same time. This is the period during which Nice (1943) heard females ’ Received 28 January 1987. Final acceptance8 July 1987. singing. 2 Present address:Serengeti Wildlife ResearchInsti- If singingby female SongSparrows results from tute, P.O. Box 3 134, Arusha, Tanzania. unusually high levels of androgensin a few birds,

1441 SONG IN FEMALE SONG SPARROWS 45 suchbehavior may be aberrant and therefore un- conducted in Discovery Park, Seattle, Washing- important. Alternatively, singing females may be ton. In eachcase, the playback speakerwas placed rarely but regularly observedunder particular and near the center of each female’s territory. Songs interesting circumstances,thus suggestinga func- were recordedon a Uher 4000 tape recorder with tion for female song. For example, Richison a microphone mounted in a 4 1-cm parabolic re- (1983) concluded that singing by female Black- flector. Sonograms of recordings were made on headed Grosbeaks (Pheucticusmelanocephalus) a Kay Elemetrics 606 1B Sona-Graph, using a functioned in family group maintenance: females 150 Hz plug-in band-pass filter to reduce am- sang most frequently during the fledgling period bient noise. and young birds oriented themselves towards their parents’ songafter becoming separatedfrom RESULTS them. Beletsky (1983a, 1983b) showed that fe- male Red-winged Blackbirds (Agelaius phoeni- THE FORM OF FEMALE SONG ceus) sang different song types in the context of Female 60194 was first observed to sing on 20 intrasexual aggression or pair-bond mainte- February 1984. The song lasted about 2 set and nance, and that these songs also differed from was composedof a seriesof clear, melodic whis- the familiar territorial song of males. tles. This female sangin bouts of from one to six In this paper, we show that singing by female songsfrom a perch above the shrub canopy. The Song Sparrowsoccurred primarily in the context songwas loud (audible from three territories dis- of territory defenseagainst female intruders. We tant, about 80 m) and resembled that of a sub- suggestthat singing by female Song Sparrows adult Purple Finch (Carpodacuspurpureus). The indicates high levels of androgens, and that such songs of 11 other females heard subsequently high levels are a normal consequenceof aggres- varied in volume, length, and complexity, but sive interactions. Androgens may be secretedin most resembled the songsof 60 194. responseto repeated or prolonged conflicts be- The female songsthat we recorded were sim- tween females for territory ownership, as dem- ilar to male songs in frequency range, timing, onstrated for male Song Sparrows by Wingfield and overall structure (Fig. 1, compare F1-4 with (1984b). Ml-2). P. Marler and S. Peters (pers. comm.) have also recorded songsfrom live-tutored, cap- METHODS tive females that had been implanted with tes- Our observations were made during a long-term tosterone (Fig. 1, Tl-2). Sonograms of record- study of the resident Song Sparrow population ings from two of these females show a simple on Mandarte Island. Mandarte is a small (6-ha), (Tl) and more complex song (T2) that nearly shrub- and grass-coveredrock in the Haro Strait, span the range of song variability that we re- approximately 64 km south of Vancouver, Brit- corded in the wild (Fig. 1). Overall, males and ish Columbia, Canada. Details of the population females sangsimilar syllable types including pure and the general methods employed there can be tones, buzzes, frequency modulated notes and found in Tompa (1964) and Smith (1981, in rapid sweeps(Fig. 1). On average, however, fe- press).From 1982 through 1986, one of us (PA) males tended to sing songs that included fewer visited the island for 2 to 5 days at least monthly different note types in each song than did males. from September to February, and lived semi- Nevertheless, the longer, more complex songs permanently on the island from March through could easily passfor male songsto a human lis- August. During this time, the locations of all tener and might go unrecognized in unbanded birds sightedwere recordedon maps drawn from populations. an aerial photograph, and special attention was Male Song Sparrowson Mandarte sing four to paid to conflicts over territories. 12 songtypes and 30 or more variations on each During the spring of 1985, PKS and SMH re- type (Hiebert, Stoddard, and Arcese, unpubl.). cordedthree singingfemales on Mandarte Island. These males sing five to 40 songs of one type, One of these females was recorded while singing alternating among variations, before switching spontaneously. The other two sang in response to another type. The females we recorded sang to a playback of songsrecorded from a male on variations the way males do, and we recorded a nonadjoining territory. An additional female one female long enough (60 songs) to discover was recorded by PKS during a song playback that she had at least two discrete song types. 46 P. ARCESE, P. K. STODDARD AND S. M. HIEBERT

females were heard singing in more than one year. In contrast, territorial males on Mandarte Island sang more or less throughout the year, with peaks during late winter, spring, and fall. Table 1 showsthat female Song Sparrowssang mainly between 20 February and the beginning of egglaying, which occurredbetween late March F2 and mid-April (Arceseand Smith, in press).Only one female (60300) was heard singing after she had begun to lay eggs.This female sangregularly kHz 6 from 7 April to 18 June 1985, usually when she -t 4 came up from her nest and before she returned F3 2 I- .,...,I. to incubate eggsor brood nestlings. Singing by females, though always uncom- mon, has been heard more often in this popu- lation when population density was high. F. S. Tompa (pers. comm.) heard a female sing in this F4 population only during the year of highest pop- ulation density during his 4-year study. This was also the only year in which he observedterritorial conflicts between females (Tompa 1964, pers. comm.). J.N.M. Smith (pers. comm.) also heard a female sing in this population in the year of highest density during the period from 1974 to 1979. No female was heard singing in this study prior to 1984, despite intensive observation. Three females were observed singing in 1984, nine in 1985, and two in 1986 (Table 1). Figure

kHz 2 showsthat fewer than the overall averagenum- 6 ber of females were observed singing when pop- 4 - ulation density was low, while more than ex- Ml 2 I pected were observed in high density years.

THE CONTEXT OF FEMALE SONG Female song was nearly always associatedwith territory defenseand it resulted most frequently when females disputed territory ownership. This

1 *ec can be seen by considering each observation of FIGURE 1. Sonogramsfrom threefemales recorded a single day or series of 2 days of singing by a on MandarteIsland (Fl-3), one from a femaleat Dis- female as an event. Of 17 suchevents, 12 (70.5%) coveryPark, Seattle(F4), and two recordedin New occurred during vigorous conflicts between fe- York by P. Marler and S. Peters from captive, live- males for territory ownership (Table 1). In these tutored, females implanted with testosterone(Tl-2). 12 cases,songs were heard from eight territorial Two male songs(Ml-2) recorded on Mandarte Island are provided to illustrate the similarity of note types females and four intruders (three neighbor ter- between male and female songs. ritory holders, one nonterritorial floater). Figure 3 showsa typical territorial conflict be- tween three females that took place over at least THE OCCURRENCE OF FEMALE SONG 3 days. Two of these females (60 194 and 60279) Singing females were rarely observed over the sang repeatedly as the third (60182) was chased study period (Table 1). Only 12 of approximately and ultimately evicted. The evicted female later 140 females were heard singing during 267 fe- settled two territories distant with an unmated male-years of observation. Of these 12, 10 sang yearling. Two additional females sang when no on only one day or two consecutive days. Two conflict was apparent. In both cases, however, SONG IN FEMALE SONG SPARROWS 47

TABLE 1. The occurrenceand context of female songin the Song Sparrow. No females were observedsinging in 1982 or 1983.

Year FellI& number 1984 1985 1986

60194 20 February: Evicting a fe- 3 April: In responseto male Not heard singing. male floater. playback. 22 February: Evicting same 15 April: Evicting a female and settling new boundary. floater. 60279 20 February: Taking over Not heard singing. Not heard singing. new territory by evicting former female owner. 60300 10 March: Taking over new 3 April: In responseto male Not heard singing. territory by evicting former playback. female owner. 7 April: Evicting a female floater, then regularly to at least 18 June. 60204 Not heard singing. 8 April: Evicting a female (Deceased) floater. 60108 Not heard singing. 25 April: On border as adja- (Deceased) cent female is evicted by a female floater. 60254 Not heard singing. 17 April: No apparent con- Not heard singing. flict. 60126 Not heard singing. 3 April: Responseto male Not heard singing. playback. 59239 (Year of hatch) 19 April: Attempting to settle Not heard singing. between establishedterrito- ries. 59114 (Year of hatch) 18 April: Taking over adja- Not heard singing. cent territory by evicting owner. 58909 (Year of hatch) 29-30 April: Near female (Deceased) floater that settles on adja- cent territory. 59133 (Year of hatch) Not heard singing. 16 March: No apparent con- flict, but settled within the previous month. 59150 (Year of hatch) Not heard singing. 3-4 April: During intense fights with female floater.

home ranges of nonterritorial females encom- males never responded to these with song, though passed part of the singer’s territory. threat notes, chatters, tchunks, and caterwauls Three additional observations of female song (Nice 1943:274) were common. Females were were made when we played a tape recording of never observed responding to intruding or neigh- male song. One of these observations was made boring males with song, though they did some- unintentionally while we were trying to stimulate times respond to these birds aggressively (i.e., a territorial male to sing. This is the only female supplant, chase, and puff-wave posture, similar (60 126) that was not also observed singing under to “puff-sing-wave” described for males by Nice natural circumstances. The two other females that (1943:274). responded to playbacks with song were 60300 DISCUSSION and 60 194, the most active spontaneous singers observed during the study (Table 1). Recent experimental studies indicate that female No other playbacks were conducted during song in plays a role in courtship, main- spring or summer, but playbacks were frequently tenance of the pair-bond and family group, and used as an aid during late winter censuses. Fe- territory defense (Beletsky 1982, 1983a, 1983b; 48 P. ARCESE, P. K. STODDARD AND S. M. HIEBERT

k O- d ’ d ’ 8 I I I I I I It 20 30 40 50 60 70

Number of Territorial Females 50m _ FIGURE 2. The proportion of females (transformed FIGURE 3. Depiction of a conflict between three fe- by arcsine square-root)heard singingin relation to the males for the ownership of a breeding territory (band total number of breeding females. The dashedline in- numbers refer to those in Table 1). Birds defend areas dicates the average proportion of females in the pop- of shrub (outlined area) surrounded by grasslandor ulation heard singing over the entire study. The data rocky intertidal. Female 60279 intruded from her pre- are heterogeneousacross years (x2 = 12.78, df = 4, vious territory (solid arrow), sang (black dots), gnd P < 0.025). chasedfemale 60 182 from her former territorv. Female 60 194 chasedfemale 60182 whenever she eitered her territory and she(60 194) sangrepeatedly (open circles). Richison 1983, 1986). However, these studies Female 60182 settled several days later with an un- have dealt only with species in which females mated yearling male (broken arrow). commonly sing. No function has been suggested for female song in specieswhere such behavior is rare (e.g., Rufous-sided Towhee, Pipilo ery- Blackbird, female songs do not resemble those throphthalmus, and Indigo Bunting, Passerina of males (Beletsky 1983a, 1983b). In others, cyanea [Nolan 19581, and Song Sparrow [Nice however, females sing songsthat are either nearly 1943, this study]). Nice (1943) believed female as well-developed as males (e.g., Black-headed song served no function in the Song Sparrow, Grosbeak, Richison 1983) or equally well-de- and that it resulted from unusually high levels veloped (reviewed in Farabaugh 1982). In species of androgens in a few abnormal individuals. In in which females rarely sing, female songs are the following discussion,we compare our results usually less well-developed than those of males, with those of Nice (1943) and speculate about and are often described as resembling those of the implications of female song in our popula- immature males (e.g., Nice 1943, Nolan 1958, tion. this study). This suggeststhat there may be a Nice (1943: 127) describedthe song of females reduced capacity for female song learning and/ that she observed as “short, simple and entirely or performance in speciesin which males com- unmusical,” with the exception of one bird monly sing but females rarely do so. (K135). On 2 April 1934, Nice (1943: 127) noted Nice (1943) defined five stagesand Mulligan that female K135 “has a special place on the (1966) four in the song development of male locust where she sings;her songis shrill and loud; Song Sparrows.These began with a soft warbling it reminds me a little of a White-throat [(Zo- stage and culminated in full crystallized song. notrichia albicollis)]. There are at least two ver- The females we recorded appeared to be nearing sions; they are not as unmusical as most female the final stage.More of their vocalizations were Song Sparrows.” The singing behavior of most songfragments than we would expectof a mature females that we have heard most closely resem- male, but they did sing some full, complex songs. bled that describedfor K135 by Nice. However, Further, in all of the female songs that we re- not all females that sang on Mandarte produced corded, internote intervals were similar to those musical, male-like songs.Sonogram Fl in Figure of crystallized male song. This suggestseither 1 representsone such song that more closely re- that: (1) practice-singing by females is not as im- sembled the songsthat Nice reported. portant in songdevelopment as in males, (2) that There is also considerablevariation in the sim- some females practice singing as yearlings, or (3) ilarity of song types of males and females across that the song learning processis somewhat dif- species.For example, in some speciesin which ferent for male and female Song Sparrows. females commonly sing, such as the Red-winged Nice (1943: 127) observed young, unbanded SONG IN FEMALE SONG SPARROWS 49 birds which she suspectedwere females singing (Arcese and Smith, in press), but variation in in fall; a female that she hand-raised also pro- reproductive successis increasedamong females duced juvenile male-like warbles. However, we (Smith and Arcese 1986). have never made such observations on color- We suggestthat, as population density and banded, juvenile females. We therefore suggest variation in reproductive successincrease, com- that practice-singing is lessimportant for female petition among females for high quality territo- Song Sparrows than it is for males, perhaps be- ries or males becomes more intense. Such com- causefemales sing fewer and simpler song types. petition commonly leads to territorial conflicts Further, the song learning processfor males and between females at high population densities females might differ if female songlearning func- (Arcese, unpubl. data). Androgen levels may in- tioned in species recognition, mate choice, or creasein females involved in prolongedconflicts, inbreeding avoidance (review in Payne 1983) as as has been demonstrated in wild male Song well as in territory establishment and defense.In Sparrows (Wingfield 1984b), P. Marler and S. this case,song learning in females might be more Peters (pers. comm.) have repeatedly found that highly developed for recognition than for per- singing can be easily induced in female Song formance. Sparrowswith testosteroneimplants. It is there- We observed singing females almost exclu- fore reasonableto conclude that conflict-induced sively during the period just prior to nest building elevations in androgen would have a similar ef- (late February to early April). This period match- fect in highly stimulated females.Androgen levels es closely the dates given by Nice (1943: 127) of in wild female Song Sparrowsare known to nor- 12 February for the earliest song and 19 April mally approachthe levels observedin males dur- for the latest. Nice (1943) also notes that Weth- ing the periods in which we and Nice (1943) erbee (cited in Nice 1943) reported a color-band- observed females singing (Wingfield 1984a, ed female SongSparrow that sangfrequently from 1984b). April through at least 17 June, matching our rec- We therefore suggestthat singing by female ord for female 60300 (Table 1). Song Sparrows is a rare, but normal aspect of Nice (1943) observedat least two females sing- female behavior that can be explained in two ing when they participated with their mates in ways: (1) mechanistically, in terms of the rela- evicting intruding birds. For example, “On Feb. tionship between circulating levels of androgens 26, 1932, K56 was singing almost constantly, and the frequency and intensity of aggressivein- whenever she was resting from chasing 120M [a teractions; and (2) evolutionarily, in terms of the male], a new arrival that morning. At times she role of female vocalizations in aggressivecon- chasedwhile her mate sang. She perched on top tests over resourcesthat affect reproductive suc- of elders and sang very loudly, often answering cess.Our conclusionsremain tentative, however, her mate’s songs” (Nice 1943: 127). Nice (1943) because the specific relation of androgen levels mentioned no territorial conflicts when she ob- to territorial conflict in females has not been served other females singing. studied. Therefore, experimental studiesare now Our observations are consistent with Nice’s, needed to test if female songsor other vocaliza- with the notable exception that 83% (10 of 12) tions (e.g., caterwauls,chatters, threat notes[Nice of the females that we heard singing were in- 1943:274]) in the SongSparrow servea territorial volved in conflicts with other females over ter- function as in speciessuch as the Blue Grouse ritory ownership. In contrast, we never observed (Dendragapusobscurus, Hannon 1980). females to sing when nonterritorial male floaters attempted to evict territorial males or to settle ACKNOWLEDGMENTS between territorial neighbors, even though such Peter Marler and Susan Peters generouslyallowed us attempts were common during the study (Arcese, to cite their unpublishedfindings and reproduce their in press). This clearly shows that on Mandarte sonogramsof female Song Sparrows. Michael Cun- ningham, Peter Marler, Bill Searcy,Jamie Smith, and Island, singing by female Song Sparrows is re- John Wingfield commented on the manuscript, and lated to competition with other females for Jamie Smith and Frank Tompa kindly discussedtheir breeding space. In this regard, our observation observationsof singingfemales on Mandarte. The Tsa- of an increase in the incidence of female song wout and Tseycumbands of Saanich,British Columbia kindly allowed us to work on their island. We were with breeding density is consistent with two ef- supportedby grants from NSERC of Canada to Jamie fects of density on breeding performance: aver- Smith, NSF of the U.S. to Mike Beecher (BNS 84- age reproductive successis strongly depressed 08053), the Frank M. Chapman Fund ofthe American 50 P. ARCESE, P. K. STODDARD AND S. M. HIEBERT

Museum of Natural History, JosselynVan Tyne Fund and Rufous-sided Towhee. Wilson Bull. 70:287- of the American Ornithologists’ Union, Canadian 288. Wildlife Service, and the Northwestern Bird-Banders NOTTEBOHM,F. 1975. Vocal behavior in birds, p. Associationto PA. SH was supportedby the University 278-332. In D. S. Famer and J. R. King [eds.], of Washington and an NSF Graduate Fellowship, and Avian biology.Vol. 5. Academic Press,. PA was supportedby a Graduate Fellowship from the PAYNE,R. B. 1983. Bird song, sexual selection, and University of British Columbia. female mating strategies,p. 55-90. In S. K. Wasser [ed.], Social behavior of female vertebrates. Aca- demic Press, New York. LITERATURE CITED RICHISON,G. 1983. The function of singingin female Black-headedGrosbeaks (Pheucticus melanoceph- AR-E, P. 1987. Age, intrusion pressure and ter- alus). Auk 100:105-l 16. ritory defence againstfloaters by male Song Spar- RICHISON,G. 1986. The singing behavior of female rows, Anim. Behav. 35~773-784. Northern Cardinals. Condor 88: 156-159. ARCESE,P., AND J.N.M. SMITH, In press. The effects SMITH, J.N.M. 1981. Cowbird parasitism, host fit- of supplemental food and population density on ness,and age of the host female in an island Song reproduction in Song Sparrows.J. Anim. Ecol. Sparrow population. Condor 83: 152-l 6 1. BELETSKY,L. D. 1982. Vocalizations of female SMITH, J.N.M. In press. Lifetime reproductive suc- Northern Orioles. Condor 84:445-447. cessin the Song Sparrow. In T. H. Clutton-Brock BELETSKY,L. D. 1983a. Aggressive and pair-bond [ed.], Reproductive success.Chicago Univ. Press, maintenance songsof female Red-winged Black- Chicago. birds (Ageluiusphoeniceus). Z. Tierpsychol. 63: SMITH,J.N.M., ANDP. ARCESE.1986. How does ter- 47-54. ritorial behaviour influence breeding bird num- BELETSKY,L. D. 198313.Aggressive response to “self’ bers?Zn L. C. Drickamer [ed.], Behavioural ecol- songsby female Red-winged Blackbirds,Ageluius ogy and population biology. Privat, Toulouse. phoeniceus.Can. J. Zool. 61:462-465. TOMPA,F. S. 1964. Factorsdetermining the numbers FARABAUGH,S. M. 1982. The ecologicaland social of Sona Svarrows(Melosoiza melodia. Wilson1on sianificance of duettinn. v. 85-124. In D. E. Mandirt; Island, B.C., Canada. Acta Zool. F&n. Goodsma and E. H. Myher [eds.], Acoustic com- 109:3-68. munication in birds. Vol. 2. Academic Press,New WINGF~ELD,J. C. 1984a. Environmental and endo- York. crine control of reproductionin the SongSparrow, HANNON,S. J. 1980. The cackle call of female Blue Melospiza melodia I. Temporal organization of Grouse: does it have a mating or aggressivefunc- the breeding cycle. Gen. Comp. Endocrinol. 56: tion? Auk 971404-407. 406-416. MULLIGAN,J. A. 1966. Singingbehavior and its de- WINGL~ELD,J. C. 198413. Environmental and endo- velopment in the Song Sparrow, Melospiza melo- crine control of reproductionin the SongSparrow, dia. Univ. Calif. Publ. Zool. 8 1:l-76. Melospiza melodia II. Agonistic interactions as NICE, M. M. 1943. Studies in the life history of the environmental information stimulating secretion SongSparrow. II. Trans. Linn. Sot. N.Y. 6: l-328. of testosterone.Gen. Comp. Endocrinol. 56:417- NOLAN, V. 1958. Singing by female Indigo Bunting 424.