J.P. MycIs 1974 Journal 19 November Arroyo Chico, Estancia Medaland, 35 Km. S of Juvando by road, Dpto. de Mendoza, Pcia. de Bs. As., Argentina. Began the morning at 0643 by running the linear grid. The Arroyo flood is up and as a result it has expanded horizontally over a 10 meter, in many places. Clouds = 5%; temperature = 12°C; a light W wind. Grid totals: Calidris fuscicollis 10; Arenaria interpres 2; Charadrius fallaxlandicus 2; Himantopus h. 3; Anas georgica 3; harus chaeulipennis. Although I cannot be certain, I suspect that the increase in water level + thus decreased suitable of habitat for fuscicollis (in that these areas which were in optimum condition for foraging are no longer available because of increased water depth, and that areas now under suitable water-depth ranges have not 'matured', given the short time since inundation.) is responsible for the uniscible # of wading flocks. We went as far upstream as (17,28) looking for concentrations of WR and found only a few small groups. A heavy % of those seen were territorial, suggesting I think that these birds are 1) either more space constant + thus less likely to respond to weather-induced variations in habitat or 2) the areas where they are territorial are less variable, perhaps by being less susceptible to weather for some reason. At 1030 we began census ing a newly placed 'grid' between sub-units 2 and 3 of the linear grid - i.e. (15/16) - for % territorial bird calculation #4. See Calidris fuscicollis sp accent, % TB book #1, Linear grid 74B following data book. The array of territories was clear and consistent throughout the morning - by 1200 we had 10 % ten. b. calculation with an average of 75%. White-rumped on the grid averaged 3.7 /sample. The grid was 80m x 15m divided into 45 5x5 in subunits and placed with the long axis along the direction of flow of the Arroyo current. I placed the grid deliberately to incorporate part of Rplp D's territory, and also to include as much Arroyo as possible. See % TB post for map of area and WR territories. 3 WR controlled the entire stretch, and only occasionally did other WR penetrate the defenses. During the calculation period and throughout the rest of the day we monitored the units for a habitat stability measurement and performed the requisite microhabitat measurements for the paleolimn measurement. The latter must wait analysis, but at 1430 there was 0% change. Water level did decrease by 1.5 cm during