Vocal Dueling among Male Marsh Wrens: Evidence for Ritualized Expressions of Dominance/Subordinance

-Male Marsh Wrens' (Cistothorus palustris) sing with immediate variety (i.e. AB CDE . . .); they progress rapidly through their song repertoires and tend to countersing with the same song types. Intensive study of two hand-reared males in the laboratory now confirms that both the song types and the song sequences are learned. Furthermore, the leader/follower roles during countersinging duels are not determined at random. In this study, Bird 1 dominated Bird 2 in physical encounters; Bird 2 often followed (i.e. matched) the song type just sung by Bird 1, but Bird 1 matched the songs of Bird 2 only when the songs of the latter were electronically amplified. The leader/follower roles in countersinging may be ritualized expressions of dominance and subordinance, respectively, and could reveal to both males and females the relative vigor of the combatants. Received 20 November 1978, accepted 26 March 1979. IMITATION plays an important role in the ontogeny of song in many songbird species (e.g. Nottebohm 1972, Kroodsma 1977), and if juveniles either remain at or return to the locality where songs were learned, interacting breeding males will possess similar songs. If a male has only one song type in his repertoire, temporal adjustments in song delivery may be used to achieve interference or avoidance (Wasserman 1977), but when males imitate several songs and develop sizeable repertoires of different song types, the potential for complexity of interactions during countersinging is escalated. Studies of Chaffinches (Fringilla coelebs), Great Tits (Parus major), Black-crested Titmice (Parus bicolor), Cardinals (Cardinalis cardinalis), Rufous-sided Towhees (Pipilo erythrophthalmus), etc., have revealed that neighboring males often respond to one another or to a tape recording (of a song from the local "dialect") with matching song types (Hinde 1958, Gompertz 1961, Lemon 1968a, b, Kroodsma 1971, respectively; see Falls and Krebs 1975 for an apparent exception to this pattern). Males of these species typically sing a song type several times before switching to another (i.e. AAAA . . . BBBB . . .), but the potential for vocal interactions is further heightened when successive songs are usually different (i.e. ABCDE . . .), as in the Marsh Wren (Verner 1975). With such a rapid interchange of song types, the roles of leader and follower in the countersinging become immediately evident. Verner (1975: 295) speculated that this song-matching during countersinging reflected "the dominance/subordinance relationships between neighbors," but because of the complexity of both the song repertoire and the interactions in the field, he could not adequately document the relationship among males. Having studied this phenomenon in the laboratory with hand-reared birds, I can now (1) confirm that both the song types and favored sequences in this complex behavior are learned, (2) reveal that the roles of leader and follower in countersinging duels are not determined at random, and (3) support the hypothesis that such vocal dueling, together with loudness of delivery, is a reflection of size, age, and/or dominance/subordinance relationships and might be I See Kroodsma and Verner (1978) for encouraged change of common name from Long-billed Marsh Wren to Marsh Wren. 506 The Auk 96: 506-515. July 1979 This content downloaded from 157.55.39.147 on Wed, 18 May 2016 06:05:48 UTC All use subject to http://about.jstor.org/terms July 1979] Vocal Dueling among Marsh Wrens 507