Vocal Repertoire of the Mexican Chickadee I. Calls

J. Field Ornithol., 61(4):380-387

VOCAL REPERTOIRE OF THE MEXICAN CHICKADEE I. CALLS

MILLICENT SIGLER FIeKEN Departmentof BiologicalSciences Universityof Wisconsin-Milwaukee Milwaukee, Wisconsin53201 USA

Abstract.--I describeacoustic structure and use of calls (excludingsong and song-like vocalizations)of Mexican Chickadees(Parus sclateri). Calls are comparedwith thoseof other North Americangray-backed chickadees. The generalcall repertoireof the Mexican Chickadee is similar to other chickadeeshowever, the "chick-a-dee" call of the Mexican Chickadeeis very differentin acousticstructure from calls of other membersof its species group. Other differencesin acousticstructure may be due to the linkage, rather than independentevolution of certain calls.

REPERTORIO VOCAL DE PARUS SCLATERI I. LLAMADAS Sinopsis.--Describola estructuraac6stica y uso de llamadas(excluyendo las cancionesy vocalizacionesparecidas a cantos)de Parussclateri. Las 11amadasson comparadascon las producidaspor otra avesde Norteam6ricadel mismog6nero. Encuentro que el repertorio en generaldel ave estudiadaes similar a la de otroscong6neres. Sin embargo,la 11amada "chic-a-di" de la especiemexicana es diferenteen estructuraac6stica a la 11amadade otros miembrosdel grupode especies.Otras diferenciasen la estructuraac6stica podrian deberse a la uni6n, en vez de la evoluci6nindependiente, de ciertas11amadas. The Mexican Chickadee(Parus sclateri) is poorlyknown comparedto the other, well-studiedgray-backed chickadees of North America. Dixon and Martin (1979) performedthe first sonagraphicanalysis of several vocalizationsof this species,and noted marked differencesfrom other chickadees.Here a more detailedsonagraphic analysis and descriptionof use of calls are provided.Songs and song-likevocalizations are treated elsewhere(Ficken 1990b). I comparevocalizations of the Mexican Chick- adeewith other closelyrelated chickadees for which sonagramsare avail- able:Black-capped Chickadee, P. atricapillus(Ficken et al. 1978), Carolina Chickadee, P. carolinensis(Smith 1972), and Mountain Chickadee, P. gambeli (Dixon et al. 1970, Gaddis 1985).

STUDY AREA AND METHODS The main study site was Rustler Park in the Chiricahua Mountains (CochiseCo.), Arizona, the site of Dixon and Martin's (1979) study. Three visits were made: 5 and 6 Oct. 1985, 15-17 and 19 May 1986, and 5-10 Oct. 1986. Recordingbegan shortly after dawn and continued until the birds showeda marked decreasein vocalizingaround noon. In October,I followedflocks, but attemptedto recordthe vocalizationsof a singlefocal bird beforemoving on to another in order to obtain some samplesof known individuals. Three to five different flockswere studied eachfall (theywere sufficientlydistant from eachother that it wasunlikely that individualsmoved between them). In May recordingwas concen-

380 Vol.61, No. 4 MexicanChickadee Calls [381 trated near the nest of one pair, but the territories of at least five other pairs were visited.Apart from the focal pair, however,vocalizations were infrequent exceptduring territorial boundaryencounters. I used a Sony Walkman Professionalcassette tape recorder,with an ElectrovoiceSoundspot microphone in 1985, and a Nakamichi CM-100 cardioidmicrophone in 1986. In addition to recordingvocalizations, as much data as possiblewere includedon their contexts.Vocalizations were analyzedwith a Kay 7800 Digital Sona-Graph(150 Hz filter bandwidth).

RESULTS Only one nest was observed(young were presenton the day it was found--15 May). As this speciesis sexuallymonomorphic and birdswere unmarked, the role of the sexesin care of the young couldnot be deter- mined unequivocally. During the non-breedingseason, mixed speciesflocks consisted of 30- 100 individuals including four to six chickadeesand numerousother species.The flocksranged over a rather large area. The chickadeescalled frequently(mainly "Chick-a-dee"calls); other speciesexcept for Pygmy Nuthatchesø(Sittapygmaea) were much lessvocal. In many casestwo chickadeesforaged within 1 to 2 m of eachother, with a third much more distant(y 10 m). Other chickadeeswere at least20 m farther away. Very little chasingor supplantingwas observed,much lessthan in fall flocks of Black-cappedChickadees (pers. obs.). I usethe call terminologyof Ficken et al. (1978) for the Black-capped Chickadee,which is basedlargely on that of Smith (1972) for the very similar repertoireof the Carolina Chickadee.The useof the sameterms doesnot imply homologynecessarily. The entire vocalrepertoire of the Mexican Chickadeemay not have been sampled,particularly somerare calls that may occuronly in specificcontexts. It is likely, however,that the major call categorieswere recorded. "Chick-a-dee"calls.--The "Chick-a-dee" call soundsquite different from thoseof other gray-backedchickadees. A detailed analysisof this call complexwill be presentedelsewhere (Ficken and Hailman, in prep.), but a brief descriptionis providedfor comparisonswith other calls in the species'repertoire. Three note-typesin this complex call are relatively common(A, C and D in Fig. l a and b). In over 1000 calls only one or two exampleswere found of a note-typethat is similar to the B note- type of the Black-cappedChickadee (Fig. lb). The sameletters are used for designationof notetypes as for the Black-cappedChickadee (Ficken et al. 1978), but at this preliminary stageof analysis,homology is not implied. The A note-typesare quite variablein pitch and duration.They have a zig-zag pattern on a sonagram,showing rapid frequencymodulation which õivesthem abuzzy quality very differentfrom callsof otherchick- adees.The B and C are more similar to thoseof the Black-cappedChick- adee.The D note-typeshows some similarities with comparablenotes of 382] M.S. Ficken J.Field Ornithol. Autumn 1990

8- C

•

Time (sec) I I 0,5 sec FIGURE1. a. call in "Chick-a-dee"complex showing A and D note-types.b. call in "Chick- a-dee"complex showing B and C note-types.c. "Hiss" (a very shortone). d. "Hiss" (a long one, showinga slight but interruptedbanding pattern). e. "Tseet." congeners,but has a much reducedbanded pattern, and thesenotes sound much harsher and noisier. As is the casewith many other chickadees,the "Chick-a-dee" call is complexwith manyvariations. Note-types occur in differentcombinations and the number of repetitionsof note-typesis also variable.This com- binatorialsystem has been analyzed in detail in the Black-cappedChick- adee (Hailman et al. 1985). "Hiss."--The "Hiss" is one of the mostunusual callsof this chickadee, both in acousticstructure and usage.The call is highly variable (two extreme examplesare in Fig. l c and d). Coefficientsof variation were very large for both lowest frequencyand duration (Table 1). For an indicationof variability,I comparethe acousticallyrather similarD note to "Hisses" from the same bird. Coefficients of variation were much less for the lowestfrequency and durationof the D notethan for the "Hiss." The "Hiss" sounds like a sudden exhalation of air. Well-defined fre- Vol.61, No. 4 MexicanChickadee Calls [383

TABLE1. Characteristicsof "Hisses"compared with the D notefrom the sameindividual.

Highest Lowest frequency frequency Duration Note type (kHz) (kHz) (s) Hiss • 7.90 2.79 0.10 n 6 9 9 C.V. 5.4 49.1 70

D note • 6.79 3.38 0.24 n 11 12 12 C.V. 8.8 8.8 30.2 quencybands are infrequentand whenthey occur they are broken,unlike the moreregular banding patterns typical of D notesof othergray-backed chickadees."Hisses" are similar to the D note-typein this species,but differ in their greatervariability and in usuallybeing uttered singlyand neverin conjunctionwith othernote-types of the "Chick-a-dee"complex. Occasionallytwo or more "Hisses"may be given,but then they usually exhibit variable inter-call intervalsrather than the more regular intervals between D notes in a series. "Hisses"are givenin a wide varietyof situations,always when a bird is perched.They are not confinedto socialcontexts, as they are sometimes given by lone birds that are temporarilyseparated from other group membersduring the fall. They are more frequent when individualsare in closeproximity in flocks.Hisses often occurred during boutsof "Gar- gles"in territorial encounters(Ficken 1990b), the apparentrecipient of the "Gargles" givesthe "Hisses." Many were recordednear the nest hole,just beforea bird enteredthe cavity. Becauseof the varied usage, it is difficult to ascribea messageto this call. "Hisses" often occurred, however, in situationswhen there was some hesitancyto locomote,or where the caller may have beenslightly fearful. "Hisses"are widespreadin parids.Thielcke (1968) reportedthem in 13 species.However, in all other parids for which the call is reported, the usageis very differentfrom that in the Mexican Chickadee.In other species,"Hisses" are usually given within the nest cavityas the parent or nestlingssway back and forth (Thielcke1968). The acousticquality of the call and the nature of the associatedmovement gave rise to the hypothesisthat it is Batesianmimicry of a snake(Pickens 1928, Sibley 1955). "Tseets."--Theseare very short,low amplitudenotes (Fig. le), that are uncommon(n = 6, but others may not have been detected).The samplesize is small, and usageis uncertain,but they seemassociated with agonisticsituations in whichthe callermay be somewhatfearful, as seemsto be the casein the very similarcall of the Black-cappedChickadee (Ficken et al. 1978). "Twitter."--The calls consistof a variable number of very rapidly utteredtransients that covera wide frequencyrange and appearas nearly 384] M.S. Ficken J.Field Ornithol. Autumn 1990

16- a b

I I I Tim•(•½•

I I 0.5 sec FIGURE2. a. "Twitter." b. "High Zees." c. "Variable Sees"--bracketsindicate the two membersof the pair; the secondbird was calling during the calls of the first bird but its calls were masked until the first bird ceasedcalling. vertical lines on sonagrams(Fig. 2a). Only five were recorded.Twitters are low amplitudecalls usedat closerange betweenmembers of a pair. Twice Twitters occurred as a bird entered the nest hole while another was still in it, an unusualcircumstance as one usually exited when another approached.These casesof a suddenconfrontation are similar to the usageof the very similar call in the Black-cappedChickadee (Ficken et al. 1978). "High Zees."--This type of vocalization,widespread in passerines,is the onereferred to as an aerial predatorcall (Marler 1955), althoughits usageis not restrictedto aerial predatorsin the Black-cappedChickadee (Fickenand Witkin 1977). In general,the acousticproperties of this call are similarto thosereported in otherpasserines: high pitchedand covering a narrow frequencyrange (e.g., Marler 1955). "High Zees"of Mexican Chickadeesare higherpitched than the correspondingcalls of the Black- Vol.61, No. 4 MexicanChickadee Calls [385 cappedChickadee (Ficken and Witkin 1977) and Carolina Chickadee (Smith 1972). Calls of theseother chickadeesshow little frequencymodulation within a note, while thoseof Mexican Chickadeeshave a zig-zag appearancein sonagrams,indicating small, but consistentintra-note fre- quencyvariations (Fig. 2b). In Mexican Chickadees"High Zees" are simply higher pitchedversions of the A note-typeof the "Chick-a-dee" complex,as is the casein the Black-cappedChickadee (pets. obs.) and the Carolina Chickadee(Smith 1972). Thus the different structureof the "High Zees" of the Mexican Chickadeeis a reflectionof the different structureof its A note.Calls givenin high risk situationswere significantly higherpitched than thoseoccurring in low risk situations(Ficken 1990a). "VariableSees."--This is the highestpitched vocalization of Mexican Chickadees(mean highest frequency = 9.84 kHz, S.D. = _+0.65;duration 0.062 s _+0.024, n = 19 from at least 4 individuals) (Fig. 2c). "Variable Sees"are quite similar to "High Zees," often having rapid intra-note frequencymodulation, and a narrow frequencyrange. However, they are of shorterduration and averageabout 1 kHz higher. Similar callsoccur in Carolina Chickadees(Smith 1972), Black-capped Chickadees(Ficken et al. 1978) and Mountain Chickadees(Dixon et al. 1970). In the Black-cappedChickadee, the samefrequency relationship holds between "High Zees" and "Variable Sees" (with about a 1 kHz differencebetween the two calls), but both calls are about 1 kHz higher in the Mexican Chickadee. "Variable Sees"were restrictedto pair interactions,and were more commonin springthan fall. In May a bird often gavethem near the nest holewhen returningwith foodfor the young(n = 20); it typicallyperched within 1 m of the nestand begangiving either "Gargles" (Ficken 1990b) or "Variable Sees," the latter often accompaniedby wing quivering. Another individual usually left the nest cavity and sometimesthe two remainedperched near each other, both giving "Variable Sees"accom- panied by wing quivering. Some calling interactionsbetween the pair lastedas long as 6 s. When both birds called,overlapping of calls sometimes occurred,or a duet in which one bird's calls directly followed the other's.In suchcases, the callsof the two birdswere very distinctive(Fig. 2c).

DISCUSSION

The two highestpitched calls of this chickadee,"Variable Sees"and "High Zees," are both used in contextsin which the receiver is within a few metersof the caller. Both have frequencycharacteristics that lead to rapid attenuation(Wiley and Richards 1982). Although the general messagesof the two calls are very different (one a predator alert, the other associatedwith pair interactions),the similaritiesin acousticprop- ertiesmay be due to selectionfavoring design features for a short trans- missiondistance. Perhaps in addition,there are limitationson the acoustic structureof very high pitchedvocalizations, as at leastin chickadees,they 386] M.S. Ficken J.Field Ornithol. Autumn 1990 often seemmuch simplerin generalacoustic structure than other callsin the species'repertoires, and consistof long stringsof similar note-types. While each call has been discussedseparately, an interlinkedsystem of calls is apparent, rather than each call evolvingas an independent entity. For example, similaritiesare strongbetween the A note of the "Chick-a-dee"call, "High Zees"and "Variable Sees."The "Hiss" shows somesimilarities to the D in the "Chick-a-dee" call. It is probably not coincidentalthat the Mexican Chickadee, the parid specieswith the broadestusage of the "Hiss," is alsothe only one in which the D seems to havesecondarily reduced its bandingpattern, and resemblesthe "Hiss," indicatinga linkage of the evolutionof the two calls. The vocal repertoiresof the gray-backedchickadees are remarkably similar. All calls of the Mexican Chickadeehave apparent homologs (based on phonologicalsimilarity) in the Black-cappedand Carolina Chickadees,the best studied North American species.Two additional calls of adults of the former specieswere not noted in the Mexican Chickadee.One ("Snarl"), occursonly in fights(Ficken et al. 1978), and as this type of aggressionwas sorare in Mexican Chickadees,its absence in my recordingsis not unexpected.The secondcall, "Broken Dees," is commonin Black-capped(Ficken et al. 1978) and Carolina Chickadees (Smith 1972), and is givenby femalesduring a part of the breedingseason that was not adequatelysampled in my study. Basedon geneticanalysis, the Mexican Chickadeeprobably is most closelyrelated to the Mountain Chickadee,and more distantly to the Black-cappedand Carolina Chickadees(Gill et al. 1989). My analysis indicates that Mexican Chickadees are more different in the acoustic structureof "Chick-a-dee" calls from the other three speciesthan are thosespecies from each other (for comparison,see sonagrams in Ficken et al. 1978, Gaddis 1985, Smith 1972). Further studiesare neededbefore extensivebehavioral comparisons can be made.

ACKNOWLEDGMENTS

I thank Robert Ficken for assistancein the field and in preparing sonagrams.Keith Dixon, Jack Hailman, StephenNowicki, and David Spectormade many helpful comments on an earlier versionof the manuscript.I am grateful for the use of the facilitiesof the SouthwesternResearch Station of the American Museum of Natural History.

LITERATURE CITED

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--, AND S. R. WITKIN. 1977. Responsesof Black-cappedChickadee flocks to pred- ators. Auk 94:156-157. GADDIS,P. 1985. Structureand variability in the vocalrepertoire of the Mountain Chick- adee. Wilson Bull. 97:30-46. GILL, F. B., D. H. FUNK, AND B. SILVEeaN. 1989. Protein relationshipsamong titmice (Parus). Wilson Bull. 101:182-197. HAILMAN,J.P., M. S. FICKEN,AND R. W. FICKEN. 1985. The "chick-a-dee"calls of Parusatricapillus: a recombinantsystem of animal communicationcompared with written English. Semiotica56:191-224. MARLER, P. 1955. Characteristics of some animal calls. Nature 176:6-8. PICKENS,A. L. 1928. Auditory protectivemimicry of the chickadee.Auk 45:302-304. SIBLE¾,C.H. 1955. Behavioralmimicry in the titmice (Paridae) and certainother birds. Wilson Bull. 67:128-132. SMITH, S.T. 1972. Communication and other social behavior in Parus carolinensis.Publ. Nuttall OrnithologicalClub No. 11. THIELCKE,G. 1968. Gemeinsamesder Gattung Parus. Ein bioakusticherBeitrag zur Systematik.Vogelwelt 1:147-164. WILEY, R. U., AND D. G. RICHARDS. 1982. Adaptationsfor acousticcommunication in birds: soundtransmission and signal detection.Pp. 131-181 in D. Kroodsmaand E. Miller, eds. Acoustic communication in birds. Vol. 1. Academic Press, New York. Received31 Jul. 1989; accepted11 Jan. 1990.