Date of Award:

1961

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Wildlife Biology

Advisor/Chair:

Jessop B. Low

Co-Advisor/Chair:

Clifton M. Greenhalgh

Third Advisor:

Allen W. Stokes

Abstract

Naturalists for many years have known that birds sing most at dawn and at dusk, but to which of many physical variables they are responding has not been completely determined. This problem has taken on importance in the field of wildlife management because calling rate has been used as an index of abundance for numerous game birds, namely the Pheasant, Phasianus colchicus( Kimball, 1949); the Mourning Dove, Zenaidura macroura (McClure, 1939); the Bobwhite Quail, Colinus virginianus (Bennitt, 1951; Rosene, 1957): and the Woodcock, Philohela minor (Pitelka, 1943).

Of the possible variables which can influence calling in birds, light intensity has received the most attention. Haecker (1916), using a crude optical light meter, found a definite and high correlation between time of beginning morning song and light intensity. In 1924 he published findings with the same conclusion after measuring light intensity photometrically. Dorno (1924), in repeating part of Haecker's work, came to the conclusion that light was significant, but that the variation in the time of beginning morning song; and sunrise was due to differences in dispersal of light rays rather than actual light intensity. This dispersal was due, in his opinion, to latitude and season of the year. Since that time many workers have been concerned with the problem . The first American to deal with light intensity as the factor that governs time of morning calling was Craig (1926). He found a close correlation between early morning song of the Eastern Wood Pewee ( Contopus virens) and the curve of civil twilight. Walker (1928) found that the length of time before sunrise a bird sings is probably dependent on the total amount of light present, but that weather factors influence song to a great extent. In agreement with these findings were those of Lutz (1931) studying singing in the House Wren (Troglodytes musculus). He found that one individual began to sing at almost the same time on each of 24 mornings. If the morning was bright, song came earlier; if couldy, it came later, but time never varies more than 15 minutes. Wiens (1960) stated that the song of the Cardinal (Richmondena cardinalis) was closely associated with sunrise during April. He recorded calls beginning 10 minutes )plus or minus 3 minutes) before sunrise during this month. Eynon (1960), in compiling field notes of the late Aldo Leopold, showed that the first morning songs of several passerine and game birds are closely associated with very low light intensities that occur during the twilight before sunrise.

Studies showing effect of light intensity on animal activity are not limited to birds. Alexander and Moore (1958), studying singing in two species of Cicada (insects), found that both are sensitive to changes in light intensity. Singing increased as the sun came up and decreased as the sun passed behind a cloud. They attempted to stimulate singing with taped song under cloudy conditions, but only one species responded.Steven (1959) showed that schools of fish occurring during daylight hours break up as light falls below 0.1 foot-candle. He stated that there was no sudden change from day to night behavior patters at an level of light; the change was progressive.

Other factors which have been shown to affect time and rate of bird calling are temperature, wind, and rain. Groebbels (1925) believed that early morning singing was a direct response to prevailing low temperatures.

This study measure the composite and individual effects of time of day, season, light intensity, wind, rain, and temperature on calling. An attempt was made to apply correction factors to make possible more standardized calling counts. Observations were made on penned Chukars to relate sex and social organization to rally calling.

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