Date of Award:

5-1-1982

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Life Sciences:Biology

Committee Chair(s)

Keith L. Dixon

Committee

Keith L. Dixon

Committee

James A. Gessaman

Committee

Ivan G. Palmblad

Abstract

Postnuptial wing molt was studied for Mountain Chickadees (Parus gambeli) and Black-capped Chickadees (Parus atricapillus) living in the Wasatch Mountains of northern Utah. The pattern of postnuptial wing molt was typical of many adult passerines. Three factors which might affect the timing and rate of molt were analyzed for these chickadees: sex, elevation and year. Molt for male chickadees was slower than for female chickadees. Male Mountain Chickadees began molt before female Mountain Chickadees. Mountain Chickadees live at higher elevations, where the frost-free season is shorter. Molt and winter territory establishment may overlap in the annual time budget of Mountain Chickadees moreso than for black-caps. This may explain the earlier, slower molt for male Mountain Chickadees. For Mountain Chickadees, the dates of onset of molt were later with increasing altitude. The start of molt was apparently not related to altitude for black-caps. If Mountain Chickadees begin to breed later with increasing altitude, molt may also begin later to minimize breeding-molt overlap in the annual time budget. The rate of molt for Mountain Chickadees increased with increasing altitudes. The opposite was true for black-caps. Living at higher elevations than black-caps, Mountain Chickadees may be more narrowly constrained by time in which to complete breeding and molt. Thus, the Mountain Chickadee's rate of molt may increase as the frost-free season shortens with increasing elevation. Perhaps black-caps are not so constrained by the frost-free season as are Mountain Chickadees. There may be less breeding-molt overlap in their longer frost-free season. Thus, the effect of elevation on the duration and date of onset of molt may be less. The dates of onset and the rate of molt showed much annual variation for Mountain and Black-capped chickadees.

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