J. Field Ornithol., 58(2):190-197 ORGANIZATION OF SINGING IN HOUSE WRENS MEREDITH E. PLATT • AND MILLICENT S. FICKEN Department of BiologicalSciences Universityof Wisconsin-Milwaukee Milwaukee, Wisconsin 53207 USA Abstract.--House Wren songsare complexand the repertoiresof individualsare large. Most of the songsin this study were composedof nine syllablesand they were most frequentlymade up of only two different syllabletypes. The number of repetitionsof a particularsyllable type varied.Syllable arrangement was alsovariable; particular syllables usuallywere not foundin only one specificpart of the song.There was frequentsyllable sharingamong birds of this population,but little songtype sharingoccurred. Often, part of the songwas sharedbut the presenceof uniquesyllables produced many differentsong types and, consequently,distinct songrepertoires among birds. A numberof theorieshave been proposed to explainthe evolutionof complexsongs and large repertoiresin birds. In House Wrens large repertoiresmay be involvedin enhancing territorial defensealthough one hypothesisrelated to territorial defense,the Beau Geste hypothesis,was rejected.Also, large repertoiresmay have evolvedthrough female choice. ORGANIZACI(•NDEL CANTO DEL REYEZUELO(TROGLODYTES AEDON) Sinopsis.--E1canto dc Troglodytesaedon cs complcjoy conun ampliorcpcrtorio. La may- orcadc las cancioncstichen 9 silabas,aunquc s61o dos dc cstasson difcrcntcs. La rcpctici6n dc una silabaparticular varia entreindividuos. E1 arrcglodc las silabastambign cs variable. No sc cncontr6silabas particulates quc cstuvicrancolocadas cn partescspcc[ficas dc la canci6n.Aunquc partc dc la canci6ncs compartida, la prcscnciadc s•labasparticulates da origen a muchascancioncs difcrcntcs y pot cndc a un gran rcpcrtorio.Sc hah propucsto variastcorias para cxplicarla cvoluciondc complcjosdc canclonesy rcpcrtorioscn aves. En cl ave cstudiadacs posiblcquc cl gran rcpcrtoriopucda scr dc utilidad cn la dcfcnza dcl tcrritorio, aunqucla hipotcsisBeau Gcstccs rcchazada.Un gran rcpcrtoriopucdc habcr cvolucionadocomo rcspucsta a la sclccci6ndc parcja pot partc dc hcmbras. Compared to most other North American wren species,the House Wren (Troglodytesaedon) has fairly complexsongs and individualshave large songrepertoires (Kroodsma 1977). The objectivesof this studyare to (1) determinesong organization and repertoire size of individuals in a local population,(2) determinethe degreeof syllableand songtype sharing in a population,and (3) test the predictionof the Beau Geste hypothesis(Krebs 1977) that songtype changes occur concomitantly with perch switches. METHODS Songsof four male HouseWrens were recordedat the Universityof Wisconsin-MilwaukeeField Station,Saukville (Ozaukee County) Wis- consinbetween 7 June and 23 July, 1982. Songswere recordedat various timesof the day (0530-1600, C.D.T.) for any particular individual. Two of the birds had territoriesin an upland apple orchard,one was located • Presentaddress.' Invertebrate Zoology Section, Milwaukee Public Museum, 800 W. WellsSt., Milwaukee, Wisconsin53233 USA. 190 Vol.58, No. 2 Singingin HouseWrens [ 19 1 in a low brushy area adjacentto an open field, and one occupiedan upland area of primarily aspen (Populustrernuloides). The territories of Birds I, III, and IV were contiguous.Bird II was locatedapproximately 100 m from the other three. All were probablywithin hearing range of one another and these were the only House Wrens in the immediate area. Althoughthe birds were not banded,individuals were easilyiden- tified by territorial behavior; they tended to sing at or near their own nestsites and only rarely enteredanother bird's territory. A Uher 4200 Report tape recorderand an Electrovoice644 directional microphonewere usedto recordthe songs.Information describing singing locationswas recordedand distancesbetween song perches were mea- sured, enabling comparisonsto be made between songtypes given and distancesmoved between songs. Intervals betweensuccessive song starts were also recorded.Sonagrams were made with a Kay 6061 B Sona- Graph at an intermediateband width setting(150 Hz). Identificationof syllableswas primarily by shape,using frequency and temporal characteristics.Letter symbolswere assignedto syllablesto facilitateanalysis. Sequences of identicalsyllable types, regardless of the numberof repetitionsof eachtype, characterizedunique songtypes. For example, AAAAABBBBBKKKK and AAAAABBBKKKKKKK were consideredto be the same song type but they were not the same as AAAAAJJJJKKKKKKK. RESULTS Songdescription and organization.--HouseWren songconsists of two parts.The introductorypart is madeup of very low amplitude"chattery" notes,but the terminal sectioncontains clearer, louder, "bubbly" notes. As the introductorypart of the songin our recordingswas too faint to be analyzed accurately,this report deals only with the louder, terminal portion.Several song characteristics (e.g., total syllablenumber per song, numberof differentsyllables per song,syllable order) variedconsiderably among birds. Figure 1 illustratesthe syllablesin the study population and Figure 2 showsseveral representative songs of four different indi- viduals,demonstrating the ways in which syllablesare combined. Of the 1993 songsanalyzed, the total number of syllablesper song ranged from 3 to 22, with a mean of 11.49 (SD = 12.06). The mode was 9. The number of different syllabletypes per songranged from 1 to 6, with a mean of 2.92 (SD = 3.10) and a mode of 2. Order and numberof repetitionsof eachsyllable type often varied in different songs,even in the same individual. Most syllableswere not specificto a particular part of the song.For example,if a certainsyllable occurredin the beginningof a particular songand was also presentin anothersong, it did not necessarilyoccur in the beginningof that other song. Syllablesranged in frequencyfrom 1.5 to 8.0 KHz. Song duration rangedfrom 0.33 to 2.48 s (N = 220) with a mean of 1.25 (SD = 0.35). 192] M. E. Plattand M. S.Ficken j. FieldOrnithol. Spring 1987 A B D E F G J K O P T U A B C D E F H I J K L i T U W•Z A B C E H I J K O Q X Y FIGURE 1. Syllablesin the songs(terminal, "bubbly" sectionsonly) of House Wrens at the University of Wisconsin-MilwaukeeField Station.(a) Bird I (b) Bird II (c) Bird III (d) Bird IV. Generally, malessang most rapidly when a femalewas closeto or in the nest. Amountof syllablesharing.--Examination of sonagramsrevealed an extensiveamount of syllablesharing. Sevenof the 26 syllablesused by the four birds were commonto all. Six other syllableswere sharedby three out of the four birds. Twelve syllablesmay have been unique to individuals.Bird I shared l0 of its 12 syllableswith at least one other individual, Bird II shared 13 of its 16 syllables,Bird III shared 14 of its 19 syllables,and Bird IV shared 11 of its 13 syllables.Coincidence indices(Dice 1945) were calculatedto show degreeof similarity of syl- lable typesbetween pairs of birds. In the equation Coincidenceindex = 2h(a + b) h = number of sharedsyllables, a --- number of syllablesof Bird A, and b -- number of syllablesof Bird B. Values of the coincidenceindex range from 0, indicatingcomplete lack of sharing of songsyllables of the two individuals,to 1.0, indicating completesharing. In this study, values FIGURE2. Examplesof House Wren songsshowing the songtype variability that may occurboth amongand within individual birds. (a) Bird I (b) Bird II (c) Bird III (d) Bird IV. Vol.58, No. 2 Singingin HouseWrens [ 193 8 0 ' ,," DE D T U J K - ; Time (sec) Time (sec) 8 , •. T U L B 1 Time (sec) T•me (sec) 8 .•. • m ' • I I I I • K B . Time (sec) B K Time (8ec) •2 I J K s T K B ø•'1½I' i ,!.•, T•me (sec) Time B 0 DE Time (sec) Time (sec) 194] m. E. Plattand M. S.Ficken J.Field Ornithol. Spring 1987 T^•Lw 1. Coincidenceindices for syllablesharing. Bird II III IV I (12) a 0.71 0.65 0.56 IX (16) 0.74 0.69 III (19) 0.69 IV (13) Total number of different syllables. rangedfrom 0.56 to 0.74 (Table 1), with a mean value of 0.67 (SD = 0.063), indicatinga relativelyhigh degreeof similarity betweenindivid- uals with regard to syllabletypes. Unique syllableswere generally locatedat either of the two endsof the songs.Both of Bird I's two unique syllableswere locatedat one end or the other of the 15 songsin which they occurred. Bird II had three unique syllables.Of the 71 songsin which they occurred,they were at the beginningor end in 47 of them. In the other 24 songs,they were near the end and each time they were followedby a syllabletype (B) which terminated the song. Bird III had five unique syllables,one of which initiated the songin 39 of the 62 songsin which they occurred. In the other 23, they were near the beginningof the song,being preceded by only one syllable (Q). Bird IV had two unique syllables.Of the 10 songsin which they occurred,they were within the bodyof the songonly twice, and in both casesa unique syllablealso began the song. Amountof songtype sharing.--Sharingof songtypes (unique syllable combinations)occurred infrequently. Of the 130 songtypes that were usedby the four birds, 120 were unique. Only one songtype was used by all of them and only two were sharedby three out of the four indi- viduals. More specifically,Bird I shared7 of its 33 songtypes, Bird II shared9 of its 37 songtypes, Bird III shared5 of its 52 songtypes, and Bird IV shared3 of its 22 songtypes. Coincidence indices of the degree of sharingof songtypes between pairs of birds rangedfrom 0.03 to 0.17 (Table 2), with a mean value of 0.09 (SD = 0.047). These indices, however,do not take into accountsongs