J.P. Myers 1974 Journal (5,21) Estancia Medaland, 35 km S. of Jvaracho, Ptdo de Madariaga, Pcia de Bs. Aires, Argentina almost invariably headed SE. This would be consistent with the observations that I made on buffle roosting (flights 10 and 11 September). The whirling flights of the different flocks appeared to have something of a segregational effect (by centrifuging?) on the flock as a whole. As far as I could tell, flocks became progressively more numerous, and the final direction of the species may have been difficult as well. However, by concentrating on following one particular flock I sacrificed part of the overview. I must admit that it was a remarkable event - hundreds of the birds engaged in various independent lots of aerial acrobatics. I suspect also that other flocks from joining fields were recruited. Equally remarkable was the suddenness with which it ended: by 1845 there were no shorebirds flying. Incredible #s of shorebirds were flying. ~ 47.25 ha (1,18) Region, Estancia Medaland, 35 km S. of Jvaracho by road, Ptdo de Madariaga, Pcia de Bs. Aires, Arg. 15 September 0945 entered the (1,18) etc region by Rte 11. Temperature this morning was 11°C at 0800, heavy fog, slight SE Gage. Numerous shorebirds present upon my arrival, and listed other species seen: S. Horchords: Vanellus chilensis 39; Pluvialis dominica 57; Ortyxolus ruficollis 31; Tryngites subruficollis 74; Calidris bairdii 2. eburn. Chauna torquata, Larus dominicanus, Larus marilgenis, Circo cinereus, Nothura maculosa, Speotyto cunicularia, Cinclodes fuscus Colaptes campestris, Pitangus sulfuraceus, Lessonia rufa, Ecomada quinulata, Columba picoguera, Mimus saturninus, Meloethorus bonacensis, Agelaius phillipsi, Pseudoleucopsar maccians, Sturnella defilippi, Anthus corvusenda, Zenotrichia capensis, Sicalia luteola, Spinos magellanicus. I remained in (1,20) for the rest of the morning, leaving at 1145. See Tryngites, Pluvialis, Vanellus egg count. Located 2 Vanellus nests w/ incubating adult (see Nest). Also see couple accent. [illegible] (5,21), Estancia Medaland, Ptdo. de Madariaga, Pcia de Bs. Aires, Argentina 1715 drove to (5,21) in order to follow roosting flights. Clouds 100%, Temp = 11°C wind light SE. Heavy fog lying over the coast, moving upon us rapidly. Reached (5,21) region at 1730 - large shorebird flock present was here, again predominately golden's, with some buffle, David's and a few Zenayga modestus. This evening the flights took off at 1745, leaving en masse as they had the evening of 14 September. But there was not the awesome simultaneity of flight which had occurred 14 Sept.