Fig.8. Tail spread (A,B) decreased with increasing air speed, although for bird 1 (A) this relationship was best represented by a cubic function, and for bird 2 (B) a quartic function (GLM; bird 1: F_1,7=17.61, P<0.01; bird 2: F_1,5=13.05, P<0.05). Tail-angle of attack (C,D) also decreased with increasing air speed, and for both birds this relationship was best represented by a cubic function (GLM; C, bird 1: F_1,7=8.36, P<0.05; D, bird 2: F_1,6=6.42, P<0.05). The angle of tail spread in some of the flight sequences for bird 1 (A) was obscured: the number of flight sequences for which tail-spread angle data were obtained, therefore, varies between 1 and 5. All other N=5. Values are means ± S.E.M.