Gymnogyps californianus February 13, 1946 Hopper Canyon, Calif. 100 yards apart, in column - the next 3 1/4+ mile behind. I was about 3/4 mile N. of Carbon Cliffs at the time; breeze very light; temp. 44 F.; sky clear. The birds rose in a rough group, the lower 3 maintaining a separate bunch. The condor milling is not nearly as regular as that of turkey vultures - condors seem to be in groups of 2 or 3 within the larger group. One flew at another 4+ times as if chasing; these "attacks" usually ended with both birds flapping 5-8 times. It is as though pursued bird climbs to get out of way - or when both lose balance they must flop to regain it. A third attacked the pursuer 3+ times in some manner but no apparent contact. 8 flaps was maximum seen; about 4/sec. The bunch broke up and 8+ milled above Rock Ridge while 2 or + headed N. and others circled over E old Calvin area. I was in open, but none seemed to notice me. Two adults returned toward Big Cave, fles gliding & giving an occasional attitude - legs dip, feet down, & landed at 9:25 in a pothole 70'+ from top of a parapet-like prominence 300+ yds. N. of Big Cave. The other condors were all out of sight by about 9:20 - rising times about 9:10 today. One of the adults squatted flat in pothole