THE organized vee formations of geese and other waterfowl have drawn attention from sportsmen and scientists for years. Lissaman and Shollenberger (1970) proposed that birds may fly in a vee to capitalize on upward rising components of the wingtip vortex currents generated by the wings of neighboring birds flying to the front and side. Franzisket (1951) felt that tip vortex energy was not important in formation flight, and Cone (1968) suggested that the tip vortex flowing from a flapping wing is quite different from that arising from the fixed wing of aircraft. Determination of the geometry of vee formations is necessary for resolution of the question of possible aerodynamic advantage in vee formation flight. We report here the first determination of the angle between the legs of vee formations of Canada Geese (Branta canadensis) and measurements of the distances between birds in formation.