Location: Alcatraz Island, S.F. Co.) (A. WEATHER: Foggy, light wind. Cold. DATE: 1/12/87 Doug Bell 10:15 - 11:00 Setting in blind or cistern. Alex & I is with me. Hordes of gulls around the island. We saw large mass fly overhead when we arrived (+500 birds). About 17 pairs are sitting around the perimeter of the cement platform - all adults. Another 12 links are sitting directly on the platform. Pairs seen evenly spaced. Some alarm calling, and map-maps when we came up. Aggression evident - short chasing to maintain spacing. Aggressive upright approaches from long distance seen in one case (3 meters). On Industry building about 70 birds are resting, Half of which are immature. Saw two choking sequences, initiated by male, followed by & flapping, on industry building. On I.S. an aggressive upright 2w. two males - each advances 2 steps - begins thrust, locks up. Both pick up sticks, drop them. Then turn away, strike ground, face-off again. Do same with a feather. Another short chase in cistern. We also saw bird w/ tail of grass when we came up to blind. Cistern - & begging from male; < 1 min. Cistern - short grass pulling. Cistern - long call, grass pulling. Cistern: aggressive upright chase (2) followed by long calling. Choking. Aggressive upright, mnr approach, choking. Long call followed. 2 choking, one grass pull. Grass pull. Meowing. Alternate grass pulling, again. Long call. Grass pull; ditto. Standoff. Upright. Upright. Oral. Mew. Long call, chase, mew. Grass pull, upright. Upright, peek. Mew & upright. Mew, chase & choke.