The Songs and Singing Behavior of the Red-Eyed Vireo

Abstract

-An audiospectrographic study of some 12,500 songs of Redeyed Vireos (Vireo olivaceus), from over 46 birds from nine states, provided data on song structure, vocal repertoires, and the birds' use of their repertoires. These songs have one or more syllables, each syllable consisting of one or more abrupt musical slurs. Each has a sizeable repertoire of syllable types, each of which may be used alone and/or with one or more other syllables to produce a number of different song types. The song type repertoires of individual birds ranged from 12 to 117 (average, 39.4). There is relatively little sharing of songs and syllable types among individuals and that which occurs is not always in proportion to the proximity of the birds concerned. A sings its different song types in a varied sequence, and rarely sings the same song type twice in succession; some types in the repertoire are sung frequently, while others are sung only rarely. No correlation was found between the song types sung, or their sequence, and the observable circumstances under which the songs were sung. Some geographic variation was found in the birds studied, but the significance of this variation is open to question. A Red-eyed Vireo in an early stage of song development has a very large repertoire of syllable types and uses them in many different combinations; as primary song is developed, some syllables and syllable combinations are perfected and others are discarded. It is probably largely a matter of chance what particular syllable and song types remain in the primary repertoire, but birds may tend not to duplicate the song and syllable types of their neighbors. The Red-eyed Vireo (Vireo olivaceus) is one of a number of passerines in which each individual has a repertoire of several to many different songs (song types, song patterns, themes, etc.), which it sings in a varied sequence, rarely, if ever, singing the same one twice in succession. Such singing was described as immediate variety by Hartshorne (1956, 1958, 1973), and may be represented ABCDEFG .... This sort of singing occurs, for example, in some other vireos (Borror 1972), the Wood Thrush (Hylocichla mustelina; Borror and Reese 1956, Borror 1964), and the Long-billed Marsh Wren (Cistothorus palustris; Verner 1975). My purpose here is to examine the songs and singing behavior of Red-eyed Vireos, and to determine the general features of the songs and the way they are sung. Lemon (1971) made a somewhat similar study, but he was concerned chiefly with the character of the songs and syllables, based on about 500 songs from only two birds; my study is based on considerably more material and it covers some aspects of Red-eyed Vireo singing not treated by Lemon. METHODS I studied 53 recordings (containing 12,509 songs), all made by me and in the tape collection of the Borror Laboratory of Bioacoustics, Department of Zoology, Ohio State University. I tape-recorded the songs at 15 inches per second, using a 24-inch parabola; most were made with a Nagra III recorder, but those made before 1960 (birds 30-49) were made with a Magnemite recorder. Forty-seven of the recordings (11,403 songs) represent 45 birds; it is uncertain how many birds are represented by the other five recordings. I numbered the birds individually and designated the five recordings representing an uncertain number of birds as bird 115. The birds studied included 2 from Maine, 5 from New Hampshire, 29 (+2 or more) from Ohio, 4 from North Dakota, and 1 each from Montana, Minnesota, Oklahoma, Texas, and Florida. Individuals are referred to in this paper by number; data on each are given in Table 1. Nearly all (about 94%) of the songs studied were graphed (with a Kay Sona-Graph, Model 7029A), as the songs were seldom positively identifiable by ear, even when the recording was played at a reduced tape speed. Song duration was measured to the nearest 0.01 s, and the maximum and minimum pitch was measured to the nearest 0.1 kHz; the time scale was based on the time of the Sona-Graph drum revolution and its circumference, and frequencies were based on a frequency scale put on the graph (by the Sona-Graph) with the songs. Measurements of songs not graphed were recorded as the average of those of other songs of the