Singing Behaviour of Blue-Winged and Golden-Winged Warblers and Their Hybrids

Abstract

1. Songs of 12 Blue-winged Warblers (Vermivora pinus), 7 Golden-winged Warblers (V. chrysoptera) and 5 obvious hybrids were studied in the field near Ithaca, New York, U.S.A. 2. The primary of the two species is distinctive. Hybrids sing one or the other of the parents' songs. Two birds had reversed songs, one a Blue-winged Warbler with Golden-wing song, the other a Golden-winged Warbler with Blue-winged song. The secondary song, sung early in the season only by disturbed birds or later in the season by undisturbed birds as well, is similar in the two species and hybrids. 3. Golden-winged Warblers and hybrids with Golden-wing vary the number of notes in their songs according to the context. Fewer notes are given after mating (especially near the female), and following encounters with other males. In most instances, the more intense the preceding encounter, the shorter the song. Blue-winged Warblers differ in that they do not change the directly at mating. A hybrid with a Blue-winged and a Golden-wing with Blue-wing resembled Golden-wings more in that they shortened immediately after mating. The only bird that lengthened his after mating was a Blue-wing with Golden-wing song. Both species and hybrids gave secondary songs following encounters with males. Secondary songs were usually given following more intense encounters than shorter versions of the primary song. Secondary songs under undisturbed conditions later in the season were more common in the Blue-wing. Flight songs which consist of secondary songs were observed only in Blue-wings and certain hybrids. Variants of this secondary occurred only in the Blue-wing. 4. The two species differed in the amount of after mating. Blue-wings had an abrupt decrease at the time of mating, Golden-wings a more gradual one. However, Golden-wings ceased singing earlier than Blue-wings and were usually silent during the parental phase. Hybrids resembled more the parent species whose they sang. 5. The sequential patterning of songs within bouts was studied in birds with Golden-wing songs. Songs beginning bouts had fewer notes than those ending bouts. Under undisturbed conditions, songs with the same number of notes tended to follow each other and there were only two types of songs per bout. However, when disturbed, there was more often skipping and more than two songs per bout. 7. A hybrid (character) index was constructed of plumage patterns of the two species and hybrids. Song form and singing behavior were also scored. Form of was not directly associated with plumage but singing behavior was. Therefore, these motivational factors are probably directly genetically controlled. 8. Evidence is presented that singing is a relatively independent tendency. Birds with Golden-wing songs give the primary when the singing tendency is strong. When the general singing tendency is weaker, either absolutely or relatively because of the influence of other tendencies, particularly escape, the is shortened. Secondary seems to occur when the escape tendency is even stronger and/or the singing tendency weaker. 9. The functions of the primary and secondary songs are different, secondary songs playing no role in mate selection. The Golden-wing has developed more complexity in the primary song, the Blue-wing in the secondary. 10. Those vocalizations termed song probably have diverse functions as well as motivations in different passerines as a consequence of different evolutionary histories.