SP Myers 1974 04 Black-headed White-rump Sandpaper 1 Km W of Farmhouse on Farmhouse Rd, Estancia Mckland, 35 km S of Junin by road, Ptoct Maduringa, Pucia de Buenos Aires, Argentina 15 January (confid) about 5 m from the car. Just flew! - I heard our camera flauge flop against the roof. Rufous backed Negrito on A's territory, + A is ignoring it. 1615 - strong NW wind, cloud cover 0%. Another bird just flew in (probably over road) - came in swooping over A's area, clicked from a rush without the other bird landing. Then the "new" bird flew up + landed at W end of A's area. [Another interlude: A flew 15 m to supplement], stayed for ~10 sec, + then flew across to the W side of the pond, where we had noted territorial behavior before, + chased by a bird that had been there off. Whether or not it is a refocusing veteran or what I don't know. - Perhaps as much as 50-60% of flock in territorial maybe more. - 1620 learned that A defends an Eastern boundary well; chased one coming from E at a spot about 15 m from the wind. The intruder then flew through, landed at W end, + was followed + chased. In addition, a bird that had been along the edge of the W end was supplanted at the same time. New Behaviour - bird being chased, particularly when the chased bird is a normal neighbor (territorial), + thus with a common boundary, runs with tail held high as bird (runs away) [This is into the wind!] High held tail may be initial way into crouch [illegible] all Upset! Birds flew, wheeled around, + have now come in again. What caused it I don't know. (an airplane perhaps). A bird landed on territorial area + began chasing immediately. The group is dispersed differently though, with most of them being down by A [last crosses the pond] instead of up at the W end of the pond. What dispersal pattern will they achieve? A bird in A's territory (now called A' because I can't be seen) made aggressive motion toward a Semipalmated Plover - ran over to SP when it began to land, but inside of supplementing ran a circle around it + began feeding again. Mistaken, 10? 1630 - A' chased bird from E at approx. p.m. pt. A used to chase. A' chasing again, same borders. Also went after solitary Microplatalon -> M finding up to belly in 160, but approaching shore. A runs towards it but quickly goes to deep in H2O, + retreats. Squawking as he went. 13 minutes since landing the original dispersal patterns appears to have been reached!