Gymnogyps californicus March 15, 1946 Hopper Canyon, Cal't low & behind the mandible - rest of head sooty the color shows through somewhat & pale sides of neck evident. 5:22, 6 near dry pool at falls, 3 in shade. Fuzzy headed jimm. somewhat alone in the group. It nibbled sand. It nibbled green glass & tossed it from into the hill several times. One adult pt. stalked another as if going to display. It put head under the other one and again - the other gave a jump & lost a bunch of down plus a 4+" feather which remained in the first one's bill. 5:25- much shifting of perches. Still at 5:30- 10 atop cliff & 4 (3 min.) on whitewash ledge. One one min. crawled flat on the ledge. Saw one sooty head peck twice at another (each time a hiss was heard). A third then peck' ed at the pecker; pecker took off followed by the third, & then the first pecked & took off after them. 5:35- sunset line crossed top of cliff above Big Cave. One or more in flight almost constantly heard or seen. One sooty head landed on at a perch where another just landed & just took off. 5:38, heard a grunt sound like a suppressed blech - I do believe the birds make hisses, grunts, & growls occasionally. Air calm since about 4:30 p.m. 5:40- only 6 in sight now - 3 on whitewash ledge & 2 atop