Calidris fuscicollis Arroyo Chico, Estancia Meekland, 35 Km S. of Juancholey road, Ptdo de Maldonado, Pcia de Bs. Aires, Argentina in which I have picked it up; the other two were in the roosting swamp + a similar spot near Farmhouse Rd. Rylo was defending a territory where it had been before - just N of subunit 24, though there was considerable intrusion by other birds (including Rylgy). I watched Ryloo for 20 minutes from 1110 to 1130. I picked it up in the usual spot - the southern part of subunit 5. But instead of concentration, foraging activity on sub 5 with a border near 20 on the S, Ryloo continued foraging upwind (i.e. south) over 75 m beyond the previous limit of its foraging activity. Not only did it receive no challenge (suggesting that its previous neighbor has departed), but it allowed another bird to work along the W side of the Arroyo from N of the 110 stake to 50 m S of 20 - in other words following the footsteps of Ryloo. However, only Ryloo did supply behind when it approached within ~10 m of Ryloo. This could hardly be called a territorial system; its only resemblance to that is from the topography of the supplementation, which was a classic slightly hard raise-squeak-flight supplant. Thus the similarity ended though, as the intruder just simply flew out over the Water + S of Ryloo, landing less than 10 m (beyond). Ryloo left then. Rylgy was between 8 & 9 again today. 20 April 3 definite WR rooting in Arroyo between 7-8, there may have been more netting at subunit 7-8 this morning, banded 6 new WR + recaptured Rygg. Its weight was up to 50g from 35g (measured 16 February) - an increase of 43%. Mean weight of WR's captured this morning was 50g (43-56). 1752 began blaring following 2nd on Ryloo at subunit 5 (see following date). At 1750 Ryloo was supplanted from the S edge and flew WR, 1755 - Ryloo was foraging N along the edge of the water when to the S came a Vanellus, also foraging at the edge. Ryloo detoured out onto the sand and around the Vanellus, keeping a 2m radius from the Vanellus. Ryloo is foraging in typical Arroyo fashion - search peck, moving quite methodically up + down the slue. No obvious 'species pairing'. Ryloo spending time on shore and in water as well, up to the pick-a-flax joint. Juvenile Zonibys approached WR. Then when a Vanellus chased the Zonibys it also spooked Ryloo - both flew down to subunit 4 + did not return. At 1820 I found a definite territorial (non-banded) WR at the S end of 8. [illegible] unit 9-1840 found a flock of 5 WR, including Roper, Rolvr,