Characteristics and Energetics of Great Egret and Snowy Egret Foraging Flights

Abstract

Abstract Flight patterns of Great Egrets (Ardea alba) and Snowy Egrets (Egretta thula) arriving at and departing two mixed-species colonies were studied in Wichita, Kansas, in May and June 2007. For 137 short-distance flights (about 200 m) at one colony, flight duration and flight distance were recorded and wing beats were counted. For 90 longer flights (about 1,200 m) at a second colony, flight durations were recorded. From these data, wing-beat frequencies and flight velocities were calculated, then wind vector addition was used to determine air speeds and examine the effects of wind velocity and wind direction on flight patterns. Using published algorithms and data from two of our previous flight line studies, the daily energetic costs of foraging flights were estimated. Flight patterns by Great Egrets and Snowy Egrets showed some similarities. For example, mean air speeds for Great Egrets (9.2 m/s) did not differ from those of Snowy Egrets (8.7 m/s). Differences between species included lower wing-bea...