Date of Award

12-1-1972

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

Abstract

Fesi ,es begin calling on the nest before the young hatch and calling increases as the time of exodus approaches. Female calls, on the nest, lire mainly in response to calls and movements of young. Females off the nest use a variety of calls and exercise complete control over the activity of the brood using mainly acoustical cues, Broody calls are significantly different between individual females and vary depending on. the situation. As young develop, female communication to and control over the brood decreases. Young are extremely vocal except when being brooded or when in alert positions. Contact calls are common and distress calls are rare. These calls arc end points of a graded system and intermediate calls occur. As young develop they become more independent and contact calls are eventually replaced by intention and aggressive calls. Development of the young is accompanied with a decrease in frequency (Hs) of the calls and a change in their structure to form a preliminary stroke and main note. Mult calls develop from the main note of con-tact calls by a decrease in its frequency below a threshold value and the addition of harmonics. During the juvenile to adult transition period, birds give juvenile, adult and intermediate calls. Juvenile calls were similar to those of adults by 18 to 19 weeks. By their first fall, birds are taking part in bouts of sexual displays and giving associated calls.

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