JPMyers 1973 Journal Grid I, Farmhouse Puddle, Estancia Medland, 35 Km S of Triancho by road, Provincia de B.A., Argentina 24 December On grid observation post by 0550 - sun just on horizon. No wind, temp = 18°C, no clouds but a thin, low morning haze hanging over the grid. My arrival did not disturb birds (judged by lack of alarm calls or bobbing), but at 0540 two ranch hands chased a herd of horses across the puddle about 125 m south of the southern end. Two other such disturbances during the morning, plus 2 gunshots. These disturbances did not appear to affect the distribution of the birds, as none flaw, nor were there any obvious movements. However, they did evoke calling and head bobbing. Especially the gunshots - virtually all the birds I could see stopped feeding and began calling. I was able to hear every species at a grid hole on the grid calling, especially: 6.4 legs. Between 0600 and 0700 I ran 11 grid counts. 3 factors appeared to be very important in the distribution of the birds this morning: 1) in lower left h corner, (0,0), (1,0), (0,1), and perhaps (0,2) [as well as just outside the grid in (1,0), (-1,1)] then a pair of Southern Lapwings have been chasing out all other shorebirds. This behavior has not been consistent enough to exclude all other shorebirds (none of them have a 0 cumulative score) but the lapwing activity is obviously interfering with foraging by other birds. The reason for this behavior appears to be that the pair of lapwings has 4 chicks foraging in that vicinity. Interestingly, the foraging efforts of the adults are not concentrated there (see ap. accent). The interference by the lapwings has spread during the morning, to a point where by 0900 it was chasing birds off of (1,1) and (2,1). The effect of the lapwing behavior spreads beyond the periphery of its defined area, apparently because of the spreading in time. White rumps and pectorals coming area on the periphery of Rosebirds forced off their feeding areas usually first fly only a short distance and land in the vicinity of other pectoral birds. This results in more territorial (bird) interactions, which brings us to 2) aggression within the pectoral. Then several (probably 5) very aggressive birds on the grid, whose aggression appears to be space specific to territorial. (see ap. accent.) And 3) - several WR also appear —except the lapwings—to be territorial. Almost all of the aggression has been intraspecific. Occasionally I see a pectoral chasing a WR but never with the space specificity of the latter —