Date of Award:

1984

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Advisor/Chair:

Keith L. Dixon

Abstract

The American Dipper (Cinclus mexicanus), an inhabitant of rapidly flowing mountain streams, is an aquatic passerine whose vocalizations have previously been undescribed. This study examines the spectrographic characteristics and contexts of calls and song in a color-banded population of Dippers. calls of adults are the Jih, Weep and Grawk calls; calls of nestlings and fledglings are the Chip and Beg calls. Adult Dippers have a limited number of call types which occupy a middle range of frequencies (3 to 6kHz) and have structural characteristics which enhance detection of vocal signals. Gradation is present between call types. Possible explanations for similarities in characteristics of the Weep call of the adult female and the begging vocalizations of nestlings are discussed. The song is variable and complex, characterized by repetition of notes, contrast between adjacent note types and a wide range of note types. Vocal and social adaptations to the stream environment are considered.

Post-feeding singing (PFS) is song given by adult birds immediately following the feeding of fledglings. Females sang following 29. 6% of feedings whereas rrales sang following 14. 6%. Average duration of singing by males (15.4 sec) was almost twice that of females (8.4 sec). Feeding bouts and other contexts of adult singing are discussed. Evidence for the functional significance of PFS and speculations on selective forces shaping its evolution are presented.

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