Calidris fuscicollis Arroyo Chico, Estancia Medeland, Pto. 35 Km S. of Trenque by road, Pto. de Madariaga, Provincia de Bs. Aires, Argentina 28 February (cont'd) 15 minute, flying off when a flock of buffle left from their communal roosting area, WR flew on to swamp. Since 17:50 I have seen small flocks of WR taking off for the roost periodically. 19:00 12 WR going from Arroyo to swamp. 19:10 another flock of 12, WC = 4000 ft in sun; 1000 ft in shade, 19:25 - 19: more. WR going toward roost. WC in sun = 3500, shade = 500. However, the curious thing about the process by which they leave is that birds arise from a 200 m (at least) stretch of arroyo, leaving + calling simultaneously (jerk) (i.e., birds lean at the same time), but other WR, between 4 or next to three departing again. Then at similar time they leave, also in flocks produced in circular fashion. 3 March 18:00 Ran linear grid. See Journal + linear grid data book. It's up dramatically (to 123 total along all of linear grid). 4 March. 5 March 07:35 - flock of 20 was flying up + down Arroyo by tower. What crash of energy, it would occur. (1) Spotted banded birds on run down linear grid. 14 of 88 WR seen landed. See reighting chart. Of particular interest: Rr-Lr, which first banded since 2/11/74, has been seen only after or subacute 2 or between 2 and 3, was found today feeding in a flock between 8 and 7. Also, Rr-Lor was seen twice: once at 08:30 in the flock with Rr-Lr, and then again at 10:30, 4 Km S. of Arroyo just near the bridge. 7 March 17:46 began linear grid count, finishing 08:17. 31 WR seen total on grid. I did not attempt to read bands, as I subsequently made a run down the Arroyo especially for that. Total of 94 WR, 13 banded, including one new one Rr-Lp. See reighting chart. Then undertook to subacute in order to follow Rr-Loo, a WR that has been on the subacute since the day of traveling (2/21/74) and certainly before I had previously noted (e.g., 22 February) that this bird was territorial. Today my observation was reaffirmed for a 60 minute following period (Linear Grid following data book, p.40). Rr-Loo behaved in an exquisitely territorial fashion, chasing off other WR whenever they intruded from as far as one end of the territory to another. Linear distance defended was on the order of 60 m. There was some confusion because its own feeding effort extended beyond the defended border into the territory of a neighbor to the N. Maximum flight in defense was 55 m. It did not chase birds off of both sides of the Arroyo. Defense flights appeared to stop at the border - 5 aggressive acts, and one retreat from neighbors territory upon being chased once recorded in 60 minutes. There appeared to be a difference in reachin to those WR flying by + continuing on, to those flying by + landing on the territory, often before