JPMYERS 1974 Journal Etania Midland, 35 Km S. of Juanchito by road, Ptdo de Madariaga, Ria de Bs. Aires, Argentina 5 September (Contd) 1630 arrived at the curve below the tower on Arroyo Chico (subunit 1-; (10,13)). Remained until 1815 observing a group of shorebirds composed of Charadrius falklandicus, Zonibyx modestus, Calidris bairdii, and Calidris fuscicollis. Although there have been shorebirds at this point on the Arroyo during previous visits this spring, until today the dominant species—overwhelmingly plovers, peeps and me—have been Larus maculipennis, rafting between boats of following the plow which is destroying Tower Herons. This afternoon they were scarce (or no more than 6 or 7 flying areas) as the plow hadn't been used for several days. So this afternoon the shorebirds were there. And the impressive thing about them was the incredible frequency of aggression. Few minutes passed without hearing some aggressive call, particularly by territorial Zonibyx and falklandicus. See appendants. If bairdii might also be territorial, but it wasn't, nor was fuscicollis. The Arroyo here is not atypical of its solitarily through the Etania. A cross-section would look: Short grass Llanos Salamon A mound of grass-covered dirt, pitted with Vizcacha holes Sand, mixed with cactus and bones Water steep, 3' bank, with some sunbless holes and worn by scratching cattle island or sand bar the mounds along the bank are ~2m above the lowest point in the Arroyo. Width of the arroyo from steep bank → steep bank ~60m. Water width varies, narrow ~10m. Depth when measuring this morning was ~ 15cm at deepest. Depending upon time of day and wind direction, there is a strip of wet, exposed mud along the border of the water, usually about 1 0.5-1m wide. Wind this afternoon was strong and due South. 8% clouds. Temperature rose to 12°C. 6 September drove to (10,13) area of Arroyo Chico, arriving 0505 AM. Placed three nets, finishing 0610, ~15 mins after horizon began to report a slow increase in light level. Temp 0430= 3°. No wind. No clouds. Local hosts formed by dawn (accurate horizon at 0703.) Although Vizcachas were in Arroyo, as usual, when I came in before 0500, no small shorebirds were present. Apparently nothing roosted at the curve last night. First falklandicus flew in from East at ~630. First bairdii flew by 640. WR appeared in small numbers shortly afterward. Zonibyx came in before bairdii. 2 Asio flammeus glided low over the foraging area not long after falklandicus