46 JP WILSON 1974 Tryngites subruficollis (13,21) Estancia Medaland, 35 km S. of Tandil by road, Pto de Madariaga, Provincia de Bs. As., Argentina. 9 November (cont'd) in this behavior (which I may have described last January) the supplantor runs at the intruder obliquely, tightening the angle of approach as it gets closer (see drawing). The chasing bird's head is held up, out, and at an angle to the object of its interest. intruder supplantor facing into page SIDE HEAD direction of movement SUPPLANTING 0702 they flew again but again landed immediately after flying low over the area. However there one or possibly 2 buffin did not fly. At least one of these is a possible fen bird. 0721 Several cup displays by now, including one just occurred in front of my death involving 2 members of a directional flock. 0741 - by now it is obvious that a considerable portion of the grid is controlled by 1 territorial buffle. It is supplanting from distances of 40 m and is very consistent. Just now the flock flew again, but this bird, 11-9-74 A did not remain on its territory. This is the largest buffle territory I have seen, covering ~1500 m². Most common supplantation behavior is 'helicopter flight': very typical when distance greater than ~15m. Flight style different from normal - a fluttering flight when the body never assumes usual flight attitude, feet are left hanging, wings held open and at the stroke not full. [illegible] Catching the early morning light the effect of the wings fluttering is quite striking and very visible. 0722 - another cup display at West of 11-9-74 A's territory, again involving members of a directional flock. 11-9-74 A went + supplant. 0831 - appears there are 3 territorial territories impinging on the grid - 11-9-74 A's and 2 others with which it shares borders: C B 11-9-74 A 25 25 25