Importance of the Daytime Flights of Nocturnal Migrants: Redetermined Migration Following Displacement

Abstract

The daytime flights of nocturnal migrants are examined in relation to the principal axes of migration (P.A.M.) based on calm nights during spring and fall in northwest South Carolina. When nocturnal flights were to the east or west of the calm night directions (30{\textdegree} spring, 232{\textdegree} fall), flights occurred the next morning basically perpendicular to these directions. Because most migrants were displaced east of their P.A.M. in spring and fall, most daytime flights were directed toward the NW, but when nocturnal flights were west of the P.A.M., flights the next morning were to the SE. The daytime redetermined migrations permit the displaced migrants to regain their migratory route by flying the shortest distance.