JPMYERS 1973 Journal Tower Llanos Estancia Medeland, [illegible] 35 Km S. of Juancho by road, Pcia de B.A., Argentina. 19 December (contd) At that time, I have watched foraging birds of all 3 species under circumstances where they do not flock. The problem can be solved logically: observation -> that birds of each species engage in territorial behavior some of the time. There are two broad classes of possible acts of hypothesis (assuming a "clean" causal relationship): 1) external features, including food type (sensitivity to density of birds, dispersion [even as patchy, variation in density, etc.], habitat dispersion, predation [e.g., through feeding behavior, sight, frequency, etc.]); 2) internal features: age or sex class, past experience, including here or breeding ground, different breeding population. Not all of these hypotheses are equally testable, and because of the very high possibility that a number of factors are interacting, a test of a series of dichotomies appears impossible. [illegible] It is possible that birds are territorial some of the time, + flock at others (in fact it is almost certain). But do all flocking birds at some time establish there or try to establish territory? First, I argue that habitat variables are not the critical factors; they may be a necessary condition for territoriality (e.g., a minimum time of habitat stability), but they do not appear to be sufficient, for I see non-territorial birds in all the habitats in the estancia in which I have seen territorial birds. With further data, I will be able to test this statement with proportions within populations & for changes in % with time during day, weather etc. These factors could be confounding an otherwise clear picture, but I doubt it. Age & sex classes may be the critical factor in determining which birds (once given the necessary habitat conditions) are territorial. In fact, they may be both necessary + sufficient. This would be unsurprising, of course, the adaptive value for territoriality. [avoiding for the moment Hamilton's suggestion that the behaviors are not adaptive] Ok well. 5850 m Grid #9 (Farmlhouse Puddle) Estancia Medeland, Pcia de B.A., Argentina Observation post On grid at 0545. [illegible] sky clear, slight W/NW breeze, temp 65°. First reading at 0600: temp 66°; clouds 0°; wind slight, NWW; Incident vertical Light = 580 fc. Temperature rose quickly during the morning, so that when I left (0930) it was 80°. Wind increased to moderate, but no clouds. Rain 7 samples. Totals (sp, ave # range) total): Pectoral 167 (4-42) 117; LwRump 7.9 (0-15) 54; Micropalama 0.4 (0-2) 3; Lylega 8.9 (3-2) [illegible] GyLegs 1.4 (0-2) 10; Wilson's Phalarope 1.1 (0-5) 8; S.Lapwing 1.1 (0-2) [illegible]; 20 December