Tringa subruficollis 09 S.P. Myers B F143 [illegible] 28 November cont'd Tower) Arroyo Chico Llanos, Estancia Medeland, 35 km S of Junincha by road, Pcia de B.A., Argentina visible on the little mesa (birds <1' high) just to the [illegible]. I get more of an impression of independence between birds watching their b ride forage than I have for buffl oos before. Tower Arroyo Llanos, Estancia Medeland, Pcia de B.A., Argentina 19 December Sampling Grid #4 saw first clear case of supplementation between buffl oos. Two buffl oos feeding in (0,0) grid (25x25 unit). Just after I began sample, and after recording that unit, one of the feeding birds flew at the other bird, a distance of less than 20m; this resulted in the bird being "attacked" flying off of the grid. Ran the grid twice. Now I am watching, and the spacing system is not at all clear cut. Frequently this morning, on the grid and around it, buffl oos are flying at one another, in something that looks like chasing. I can hear no vocalization, and it does not look terribly aggressive like a Pied-billed Gull. But the bird being flown at usually goes away. And the chaser will then follow. For example, one bird 15 m from tower that has, within last 10 , chased 2 other buffl oos away from this area. It remains feeding by itself. Now flying over again, loading, and flying at running at another bird, this time I may have heard a little sound just enough to decipher. Still flying - and ended in chasing other bird away. This sequence took ~5 sec, at spread over ~25 m. this bird is centering his activities just to the S of a patch of durangoillo. Again - another supplementation, this time ~50m away; the buffl oo flew the distance, with the bird being chased flying before the chaser reached his area. The chaser flew back to the center of his area. Then he immediately went toward a 3rd bird that had unbundled from the opposite direction E. This interaction was more intense, but unfortunately I did not have my binoculars on the birds. I say intense because they both made a series of hopping motions as if each other, visible from here only as a series of fast 6" or so jumps. Third (both birds were doing it). I have shifted my focus to another bird in the (5,8) grid, which flew from there with the (0,0) [25x25m] unit immediately at another bird, which then left. This is a distance of over 30m. And between this bird's original site and the bird he was chasing, perhaps slightly removed from being directly between, was a 3rd buffl oo, not chased. For the next few minutes