The Vocalizations of the Slender-Billed Wren (Hylorchilus Sumichrasti) Who Are Its Close Relatives?
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528 ShortCommunications [Auk,Vol. 104 TRIVERS,R. L., & D. E. WILLARD. 1973. Natural se- Blackbirdsby egg size and laying sequence.Auk lection of parental ability to vary the sex ratio of 102: 298-304. offspring.Science 179: 90-92. WEATHERHEAD,P. 1985. Sex ratios of Red-winged Received4 August1986, accepted25 January1987. The Vocalizations of the Slender-billed Wren (HylorcI•ilus sumicI•rast•3: Who Are Its Close Relatives? JOHN WILLIAM HARDY1 AND DALE J. DELANEY2 'FloridaState Museum, University of Florida,Gainesville, Florida 32611 USA, and 2944North LaymanAvenue, Indianapolis, Indiana 46219 USA The Slender-billed Wren (Hylorchilussumichrasti) is crophoneamplifier, and Sennheiser K3U/ME-88 uni- one of the rarest and least-known members of the directional electret condensormicrophone. He was family Troglodytidae.It is endemicto Mexico and has attempting to record the song of a Black-facedAnt- restrictedgeographic and ecologicaldistributions. The thrush (Formicariusanalis) when a Slender-billed Wren speciesis known only from a few localitiesin central burst into song almost underfoot. He had encoun- westernVeracruz (and possiblyadjacent northern Oa- tered this speciesand heard it a few days earlier at xaca), and from a small area 26 km north of Ocozo- nearby Amatlan, also south of but nearer Cordoba. coautla, Chiapas (Crossin and Ely 1973). First de- Over the next 10 min he recordedseveral songs and scribedin 1871 by Lawrence(reference not seenby call notesand gave accompanyingdata on the tape. us), who placed it in the genus Catherpeswith the His recording is now on Florida StateMuseum Master CanyonWren (C. mexicanus),it was then known only tape No. 782, cut 1. from Veracruz. Nelson (1897) erected the new genus The songsof the Slender-billedWren and Canyon Hylorchilusand stated that it seemedto be interme- Wren (Fig. 1) are very similar spectrographically,and diate between Catherpesand Microcerculus,the night- to the ear. Both consistof a seriesof rapidly descend- ingale wrens. In 1925 W. W. Brown collecteda series ing, mostlyL-shaped figures given until the bird seems near Presidio, Veracruz. The last specimenstaken in to run out of breath. The figures are clear whistles Veracruz until 1985 were those obtained by Chester similarlyinflected in both species.The call notes(Fig. Lamb in the years 1942-1945 and now in the Moore 2) are also similar, consistingof sharply and down- Laboratoryof Zoology, Occidental College, Los An- wardly inflected, abrupt, shrill whistles, quite unlike geles,California. Crossin and Ely (1973)described the call notes we have heard from other wren species. disjunctpopulation first discoveredby SantosFarfan Most importantly, the songsof these two speciesdo B. (in the field with Allan R. Phillips) in Chiapasin not resemble closely the songsof any other wrens. December1969. Crossin and Ely named the new sub- The call notes(Fig. 2) were both recordedin the same speciesH. s. navai.Their paper was accompaniedby context,namely, after the singing birds had been ex- a color plate of the bird by John O'Neill. The Slender-billedWren is apparentlyconfined to midelevations(around 760 m) in steep hill country coveredby lush tropical forest, of semideciduousor evergreenaspect. All known locationsof occurrence are characterizedby extensivelimestone outcropping and heavy undergrowth.The bird remainsat or near ground level and foragesamong the rocks. Crossinand Ely (1973)offered what seemsto be the first mention of voice, though not song, of this wren. They mentioneda Canyon Wren-like call, described as a "loud metallic 'peenk' that the bird uttersat in- tervalswhile moving about."They reportedthat when callingthe bird performsa bouncingcrouch similar Fig. 1. Top: song of Hylorchilussumichrasti. FSM to that of the Canyon Wren. 782-1-1.See text for details.Bottom: song of Catherpes On 29 April 1985 at 1000,one of us (Delaney)was mexicanus.FSM 156-6-1. Anza Borrego Desert, San exploringlimestone hills between 10 and 15km so•:th DiegoCo., California,17 April 1976,by Luis Baptista of Cordoba,Veracruz, Mexico. He carrieda SonyTCM- and Hardy (1977). (Sonagramsmade on Kay Sona- 5000 cassettetape recorder(Mineroff modified),mi- graph 7029A with 300 Hz filter.) July1987] ShortCommunications 529 6 0 1 TIME IN SECONDS Fig. 2. Left: Call of Hylorchilussumichrasti. Right: Call of Catherpesmexicanus. See Fig. 1 for details. posedto playbackof their songs.Each individual then abruptly stoppedsinging and approached,soon giv- ing the calls.We believe thesemight bestbe referred to ascontact calls, given asif the birds were searching visually and vocally for the intruder. Moreover, al- Fig. 3. Threesongs of Salpinctesobsoletus. FSM D-20- though not shown in the figures,both the Slender- 7-1, near Escondida, Nuevo Leon, Mexico, 1 June 1969; billed and the Canyon wren subsequentlybegan to Ben B. Coffey, Jr., and Hardy (1977). See Fig. 1 for sing an alternate song that consistedof fewer but other details. moresustained and intensephrases in the descending pattern of the first song type. The Canyon Wren alsohas a mewing call some- in Salpinctes.The A.O.U. (1983), however, maintained times uttered immediately after it singsits primary Salpinctesas a monotypic genus,containing the Rock song.The mews, in fact, are often given as the ter- Wren (S. obsoletus).As can be seen in individual Rock minal figuresof songs.Such calls have not beenheard Wren song types (Fig. 3), the three song types are from the Slender-billed Wren. On the basis of their different from each other and all are different from vocalizations and general external appearance, we songsof Catherpesand Hylorchilus.Furthermore, in a think the Slender-billedand Canyonwrens are close song bout a Rock Wren sings such phrasesin long relatives. sequence,varying their order, pausingtypically 2-5 Crossin and Ely (1973) reported that the Slender- s betweeneach song and often continuingfor several billed Wren had only 10 rectricesvs. 12 in the Canyon minutes. The characterof song cadenceis thrasher- Wren. There is, however, precedentin birds, even in like (Toxostomaspp.). In contrast,Canyon and Slen- closely related passerines, for variation in rectrix der-billed wrens sing essentiallythe samesong type number (Stresemann and Stresemann 1966). Vaurie repeatedlyand seldom in a steady, long sequence (1980) found considerable variation, from 6 to 10, in (eachburst of descendingcomponents constitutes a the numberof rectricesin ovenbirds[Furnariidae; e.g. completesong and is followed at highly variable in- Sylviorthorhynchus(p. 55) and Synallaxis(p. 100)].Van tervalsby a rendition of the sameseries). Thus, song Tyne and Berger (1971) noted intrafamilial variation comparisondoes not supporta closerelationship be- in rectrix number and even a difference in the number tween Salpincteson the one hand and Hylorchilusand of rectrices between the male and female Common Catherpeson the other. Peafowl(Pavo cristatus). The CanyonWren is a long- Nelson's (1897) opinion that Hylorchilusmight be tailed inhabitantof open rockysites in lightly wood- allied with Microcerculus,the nightingale wrens, was ed regionswhere undergrowthis scant.The Slender- next consideredon the basisof song.The songof the billed Wren is an extremelyshort-tailed bird, similar Nightingale Wren (M. philomela),which rangesfrom in body/ tail proportionsto other tropicalforest wrens southern Mexico to Costa Rica, consistsof clear, whis- of the genera Henicorhinaand Microcerculus,for ex- tled notes(notes meaning soundsof constantpitch) ample. We suggestthat this short-tailedcondition is sung in vigorous, emphatic, long sequences(hear a derived state (unique in wrens) correlated with the Hardy 1977). They are not, however, uttered at a limited flight mobility necessaryin its densehabitat steadilydescending pitch, but rather wander up and and that having fewer rectricesis a correlateof this down the musicalscale quite unlike the songof any condition. other bird known to us (Fig. 4). The Scaly-breasted We have studied the arrangementof Mayr and NightingaleWren (M. marginatus),which rangesfrom Greenway(in Peters1960), who submergedCatherpes Costa Rica into South America, also sings whistled 530 ShortCommunications [Auk, Vol. 104 Catherpes,Hylorchilus, and Microcerculusand dissimi- larity of Salpinctes. Microcerculuslooks strikingly like a miniature Hy- 1orchilus,with disproportionatelylarge feet (long toes) and very slender, long bills in both (Peterson and Chalif 1973: plate 33). This overall similarity of the birds and the booted planta tarsusin both suggest Fig. 4. Portionof a songof Microcerculusphilomela. that despite song dissimilaritiesfurther investigation FSM D-20-19A-1, Palenque Ruins, Chiapas, Mexico, of possible affinities between Hylorchilusand Micro- 19 May 1969,and Hardy (1977).See Fig. 1 for other cerculusis warranted, but is beyond the scopeof this details. paper. We recommend that Hylorchilusbe submergedin notes (not illustrated here), but they are long sus- Catherpes,but that Catherpes,Salpinctes, and Microcer- tained, with long internote intervals, and are deliv- culusbe maintained as separategenera. eredin a remarkablysubtle pitch descent (hear Hardy 1977).The resultingsong resembles even lessthe song LITERATURE CITED of Catherpesand Hylorchilus. In further consideration of these four genera of AMERICAN ORNITHOLOGISTS' UNION. 1983. Check-hst wrens, one of us (Hardy) studiedthe descriptionsof of North American birds, 6th ed. Washington, external anatomy given by Ridgway (1904), study D.C., Amer. OrnithoL Union. skins,and