Degree Name

Master of Science (MS)

Semester of Degree Completion

1972

Thesis Director

Lawrence Barrie Hunt

Abstract

Nocturnal activity (Zugunruhe) of eight caged, radio-tagged thrushes (Hylocichla spp.) was compared by signal analysis with the occurrence of migration in 16 free, radio-tagged thrushes over a 37-night period during the autumn of 1970 in central Illinois. The study was conducted to determine the extent of synchrony of Zugunruhe and migration in these nocturnal migrants in fall. Zugunruhe frequently occurred on nights when there was no migration, but migration occurred only on nights when at least 50 per cent of the caged birds were active. Except for one departure which was atypical in several respects, migration occurred only when 1) the sun was discernible at sunset, 2) no rain fell during the 12 hours preceding sunset, nor between sunset and sunrise, 3) cloud cover was less than 50 per cent between sunset and 23:00 CST, 4) surface wind speed was 1 mph or less between sunset and 23:00, 5) there was no north component to the surface wind between sunset and 23:00, and 6) no cold front passage occurred from 3 days before to 1 day after. Unlike migration, Zugunruhe occurred under a wide range of weather conditions. Zugunruhe tended to occur sooner after capture than migration, it tended to be discontinuous, it usually began later in the evening, and was of shorter duration than the average migratory flight. One house sparrow, a non-migrant species, was also recorded and found to be essentially inactive at night. Zugunruhe appeared to be a feature of the caged migrant thrushes, although its occurrence did not coincide perfectly with migration of free thrushes.

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