Premigratory Behavior and Orientation in Blue-Winged Teal (Anas discors)

Abstract

NUMEROUS investigations have been made on avian behavior during migration. Almost all sight, sound, and radar observations of migrating birds show good correlations with weather conditions (Hochbaum, 1955; Lack, 1963). Orientation studies of caged birds during migration indicate that birds utilize celestial cues (Kramer, 1952; Sauer, 1961; Hamilton, 1962) as do directions taken by released birds (Matthews, 1961; Bellrose, 1963) and homing experiments (Matthews, 1955; Kramer, 1957). Recordings of caged birds show premigratory nightly unrest and indicate a bird's physiological readiness to migrate. Although these studies enhance our understanding of avian behavior during migration, information is scarce on the bird's activities on the breeding grounds prior to and during periods of migration. The objectives of this study were 1) to ascertain if any behavioral changes took place prior to as well as during migration, 2) to determine if these were associated with specific weather patterns, and 3) to see if all birds under observation reacted at the same time and in a similar manner to the same environmental conditions. The investigation included more than 340 hours of observations of birds in the field, of wild birds placed in orientation cages, and of a group of hand-reared birds in a large flight pen. The study was conducted with Blue-winged Teal (Anas discors) during the summer of 1963 and 1964 on the Delta Marsh, a large waterfowl breeding area at the southern tip of Lake Manitoba in Manitoba, Canada.