Troglodytes Aedon Beani): Song Structure, Repertoires, and Song Sharing
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J Ornithol DOI 10.1007/s10336-013-1008-6 ORIGINAL ARTICLE Vocal behaviour of the island-endemic Cozumel Wren (Troglodytes aedon beani): song structure, repertoires, and song sharing J. Roberto Sosa-Lo´pez • Daniel J. Mennill Received: 19 October 2012 / Revised: 15 July 2013 / Accepted: 16 September 2013 Ó Dt. Ornithologen-Gesellschaft e.V. 2013 Abstract Documenting the diversity of vocal behaviour island-endemic songbird, and for helping to clarify the across different avian taxa is key to understanding the taxonomic status of Cozumel Wrens. ecology and evolution of complex behaviours. Unique to Cozumel Island in the Mexican Caribbean Sea, the Cozu- Keywords Cozumel Wren Á Song repertoire Á mel Wren (Troglodytes aedon beani) provides an oppor- Song sharing Á Syllable repertoire Á Troglodytes Á tunity to investigate how isolation influences complex Vocal behaviour cultural traits. Most aspects of the biology, natural history, and taxonomy of Cozumel Wrens are unknown. In an Zusammenfassung attempt to better understand the Cozumel Wren’s biology, we provide the first description of the songs and the vocal Stimmverhalten des inselendemischen Cozumelzaunko¨- behaviour of this island-endemic bird. Based on more than nigs (Troglodytes aedon beani): Gesangsstruktur, 700 h of recordings, including more than 36,000 songs, we Lautrepertoires und Strophentypenverteilung describe the fine structural characteristics of male Cozumel Wrens songs, and explore patterns of repertoire organiza- Die Dokumentation der Diversita¨t des Stimmverhaltens tion and song sharing. Cozumel Wrens sing songs com- u¨ber verschiedene Vogeltaxa hinweg spielt eine Schlu¨s- posed of highly variable syllables, with prominent trills at selrolle beim Versta¨ndnis von O¨ kologie und Evolution the end of each song. Each bird has a limited repertoire of komplexer Verhaltensweisen. Der Cozumelzaunko¨nig songs, which they create by recombining a restricted (Troglodytes aedon beani) kommt nur auf der Insel number of syllable and trill types. They repeat a song type Cozumel in der Mexikanischen Karibik vor und bietet several times before switching to a different one, with somit eine Gelegenheit zu untersuchen, inwieweit Isolation some variation in the number of times they repeat specific komplexe kulturelle Merkmale beeinflusst. Die meisten elements. Cozumel Wrens share more song types with Aspekte der Biologie, der Naturgeschichte und der Taxo- neighbours than distant individuals. Syllable sharing, nomie des Cozumelzaunko¨nigs sind noch unbekannt. Fu¨r however, is equivalent between neighbours and distant ein besseres Versta¨ndnis der Biologie des Cozu- individuals. Our results provide important data for future melzaunko¨nigs stellen wir hier die erste Beschreibung der research on the ecology, evolution, and behaviour of this Gesa¨nge und des Lautverhaltens dieser inselendemischen Vogelart vor. Auf der Grundlage von u¨ber 700 Stunden Aufnahmematerial, darunter mehr als 36.000 Gesa¨nge, beschreiben wir die Feinstruktur der Gesa¨nge ma¨nnlicher Communicated by T. Friedl. Cozumelzaunko¨nige und untersuchen die Muster von Repertoireaufbau und Strophenverteilung innerhalb der J. R. Sosa-Lo´pez (&) Á D. J. Mennill Population. Die Gesa¨nge der Cozumelzaunko¨nige bestehen Department of Biological Sciences, University of Windsor, aus hochgradig variablen Silben, und jeder Gesang endet in Biology Building, 401 Sunset Avenue, Windsor, ON N9B 3P4, Canada einem markanten Triller. Jeder Vogel hat ein limitiertes e-mail: [email protected] Gesangsrepertoire, das durch die Kombination einer 123 J Ornithol begrenzten Anzahl von Silben- und Trillertypen gebildet off the northeastern coast of the Yucatan Peninsula in wird. Ein Strophentyp wird mehrmals wiederholt, bevor zu Mexico (Fig. 1). Cozumel Wrens are common in the forest einem anderen gewechselt wird; dabei variiert die Anzahl habitat on this island, wherever there are cavities suitable der Wiederholungen spezifischer Elemente. Cozu- for nesting (Sosa-Lo´pez, pers. obs.), and they adapt well to melzaunko¨nige haben mehr Strophentypen mit ihren low-density human settlement (Brewer 2001; Kroodsman Nachbarn gemeinsam als mit weiter entfernten Individuen. and Brewer 2005). Despite their restricted distribution, Allerdings haben Nachbarn a¨hnlich viele Gesangselemente they do not hold a threatened status (Brewer 2001; Kro- gemeinsam wie weiter voneinander entfernt lebende Indi- odsman and Brewer 2005). The isolated, island-endemic viduen. Unsere Ergebnisse liefern wichtige Daten fu¨r die status of Cozumel Wrens makes them an interesting subject weitere Erforschung von O¨ kologie, Evolution und Ver- for studying vocal behaviour. halten dieses inselendemischen Singvogels und ko¨nnen zur Animals that live on islands often express different traits Kla¨rung des taxonomischen Status des Cozumelzaunko¨nigs compared to their mainland counterparts (Mirsky 1976; beitragen. Baptista and Johnson 1982; Catchpole and Komdeur 1993; Pa¨ckert and Martens 2004; Baker 2006; Baker et al. 2006). For the complex songs of birds, this is manifest in multiple Introduction ways, where island-living birds sometimes exhibit patterns that contrast with mainland-living species. Some island The diversity in vocal behaviour across the songbirds populations have songs with a simple and highly variable provides a rich source of material for biologists interested structure (e.g. Certhia familiaris, Baptista and Johnson in the ecology and evolution of complex cultural traits 1982); some have unusually small repertoire sizes (e.g. (Catchpole and Slater 2008). To understand variation in Meliphaga virescens, Baker 1996); some have large rep- these complex characters, it is necessary to document and ertoire sizes and sing novel songs unknown on the main- describe the vocal behaviour and song structure for each land (e.g. Gerygone fusca, Baker et al. 2003); and others species (e.g. Mann et al. 2009). Quantitative research on have songs with simpler structures, but with larger reper- avian vocal behaviour also helps to inform taxonomists, toires (e.g. Acrocephalus sechellensis, Catchpole and conservation biologists, and wildlife managers interested in Komdeur 1993). Due to the complex vocalizations of the characterizing and protecting biodiversity, particularly in wrens—a group that exhibits some of the most complex the tropics, where biodiversity is poorly surveyed and voices of any organism on Earth (Van Horne 1995; Mann under increasing anthropogenic threat (Kroodsma et al. et al. 2006, 2009)—research on island-living wrens pro- 1996; Tubaro 1999). vides an intriguing opportunity to understand how isolation In this study, we analyze the vocal behaviour of Cozu- influences complex cultural traits. mel Wrens (Troglodytes aedon beani). These small, active Most aspects of the biology of Cozumel Wrens, birds are restricted to Cozumel Island in the Caribbean Sea including their vocal behaviour, are undescribed. A few anecdotal descriptions of their vocalizations exist. Some authors suggest that Cozumel Wren songs are similar to Northern House Wren and Southern House Wren songs, but ‘‘fuller’’ or ‘‘richer’’, and without trills (Howell and Webb 1995; Brewer 2001; Kroodsman and Brewer 2005). The lack of behavioural data is not restricted to Cozumel Wrens; among the ten recognized species in the genus Troglodytes in North and South America (American Ornithologists’ Union 1998; Banks et al. 2006; Chesser et al. 2010; Remsen et al. 2013), quantitative descriptions exist for only Northern House Wrens (T. aedon) and Pacific Wrens (T. pacificus; Platt and Ficken 1987; Van Horne 1995). The dearth of quantitative studies of Troglodytes vocal behaviour may be due to their elaborate songs (Platt Fig. 1 Map of Cozumel Island, Mexico, with four triangles showing and Ficken 1987; Kroodsma 1980; Van Horne 1995). For the locations where recordings of Cozumel Wrens were collected example, male Northern House Wrens attach different during this two-year field study: 1 north of San Miguel de Cozumel, 2 introductory notes to songs, presenting challenges to 6 km north of kilometre 5.5 of Carretera Transversal, 3 Pueblo attempts to classify song types (Platt and Ficken 1987; Fantasma, and 4 near the southwestern edge of the island. Map at upper left shows the location of Cozumel Island, 18 km off the Johnson 1998), while Pacific Wrens create new song types eastern coast of the Yucatan Peninsula continuously, so estimating an exact song repertoire size is 123 J Ornithol very difficult (Van Horne 1995). Thus, it is unclear whether periods fell during the breeding season, and wrens were Troglodytes wrens have fixed song repertoires, or whether actively singing and engaged in reproductive activities they use a repertoire of syllables to create their variable and throughout both field expeditions. In total, we followed the complex songs, or whether both types of repertoire are vocal behaviour of 23 males: 9 males recorded only in evident in different species. 2010, 12 males recorded only in 2011, and 2 males Like their songs, the taxonomy of Cozumel Wrens is recorded in both 2010 and 2011. We recorded wrens at four enigmatic. Cozumel Wrens are thought to belong to a locations on the island (Fig. 1): (1) one bird north of the group known as the House Wren complex, together with ‘‘San Miguel de Cozumel’’ (20°320N, 86°550W; recorded in Northern House Wrens (T. aedon), Southern House Wrens 2010); (2) two birds 6 km north of kilometre 5.5 of (T. a. musculus), Brown-throated Wrens (T. a. brunnei- ‘‘Carretera Transversal’’