JP Myers 1973 Calidris melanotos Grid 1 (Farmhouse Puddle), Estancia Medland, 35 Km S of Trencho by road, Pcia de Bs Aires, Argentina 26 December notable for the frequency of Pectoral interactions, among them containing more than 50% of recorded acts this morning. The correspondence between sites of aggression recorded today and manipulation from 24 December of the territory of the (3,2), (4,3) bird (see map 24 December) is particularly striking, and suggests either that the same bird is involved, or that microtopographic features in habitat are very important in determining territorial boundaries as both. Because of rain, which made observation impossible, I left the grid at 0730, returning at 1400. Rain during that period exceeded 10 mm. It was raining when I returned. I was struck by the fact that 2 pectorals, one in (4,6) and another in (1,2) were flying away from the pond and in grasses. Is this a response to rain? @ 1425 - two pectorals in lower right hand corner of the grid are not behaving territorially as far as I can tell. Both feeding, quite close. @ 1433 rain stopped. 1436 first case of territorial interaction among pectorals. In fact I am surprised by the lack of any so far. @ 1437 a pectoral chasing out other in (1,0) where I had noted none territorial once before. Is it one of them, changing its behaviour? Has someone returned? It appears to be related to the rain, as the cessation of rain has been followed almost immediately by a resumption of territorial activities. Is this related to my observations above of birds feeding in the grass? 1440 territorial behaviour in pectorals in (3,5). 1515. One very definite contested area in the middle of (0,1) unit, between a diagonal between (0,1) and (3,2). One of the birds on which I have following data (1445-1715) controls the lower half of the diagonal appears to control the upper half. 1720 fighting again. The bird of the lower half drove the other up. 27 December On grid at 0600 Did not sample. @ 0700 so far have seen a number of territorial interactions in Pectorals, in particular the area in (1,5) - (3,5). There is a bird whose territory extends from (8,0) pond above (3,5) - at least 10 m to 5 of end of grid, then it curves around including (3,5), (2,5), (2,4) and perhaps into (1,5). Another boundary near (1,3) stake, another almost certainly near 1,6 stake, Pectoral above (3,5) area inhabiting. In (3,5) a Pectoral has come over from (1,4) + is "fighting" with the Pectoral that was already there. They are head waving at one another, almost touching their bills and poking at