Repeat and Serial Singing Modes in American Redstarts (Setophaga ruticilla): A Test of Functional Hypotheses

Abstract and Summary Male American redstarts (Setophaga ruticilla) exhibit two modes of singing: repeat mode, characteristic of the early stages of breeding prior to arrival of females and before nesting; and serial mode, which prevails later when nesting has commenced and thereafter. Repeat mode consists of the repetition of a single song type, usually a song that has an “accented” ending such that the terminal phone is not repeated. The remainder of a male's repertoire is sung serially without much immediate repetition, and these songs usually do not have unrepeated endings (“unaccented”). Two examples of each mode were presented to territorial adult ( 2 years old) males, both early in the season when most often they were singing repeat mode, and later in the breeding cycle, when males more often sang serial mode. Earlier studies hypothesized different functions for these modes and one study claimed a difference in response during playback. In the present study, there were no distinguishable differences in responses by males to either singing mode, nor between the two modes at either time during the breeding season. We discuss the results relative to the earlier claims and to alternative functional hypotheses. Zusammenfassung Männliche Schnäpperwaldsänger (Setophaga ruticilla) haben zwei Singformen: Wiederholungsgesang (WG), in dem Wiederholung vorherrscht und der einen markanten Schluß hat, sowie der Reihengesang (RG), der ohne auffällige Wiederholungen Themen aneinanderreiht. WG ist typisch für die Zeit vor der Ankunft der Weibchen, RG für die Zeit ab dem Nestbau. Revierbesitzenden Männchen (über 2 Jahre alt) wurden beide Singformen vorgespielt, sowohl wenn sie selbst WG wie wenn sie RG sangen. Entgegen den Erwartungen fanden sich keine Unterschiede in den Reaktionen auf die jeweils vorgespielten Gesänge.