mjm@oliven.olivetti.com (Michael Mammoser) (06/06/90)
On Saturday, 2 Jun 90, I helped the San Francisco Bay Bird Observatory with their yearly census of the California Gull colony; one of two colonies in the south bay. I understand that these are the only breeding colonies of California Gulls that are west of the Sierra Nevada mountains. Apparently, this colony started about five years ago and has been growing by leaps and bounds. Initially a small colony of maybe 100 nests; it now numbers over 1000 nests (maybe 1500). Every year SFBBO counts eggs and chicks to determine the breeding success of the gulls and the amount of increase in the size of the colony. The colony started modestly on a sandbar/ dike that is isolated in a salt pond by water. It has spread to include two sandbars/dikes, and is now expanding along the dike on which vehicles drive into the area. Four of us met at SFBBO headquarters and loaded the skiff onto the pickup truck. This was our means of getting to the main part of the colony. We had to go through two locked gates to get to the colony which, though formerly a duck hunting club, is now on the San Francisco Bay National Wildlife Refuge. The last part of the drive was tricky, as we had to gingerly maneuver our way around the nests occupying the drive-in dike. We boated over to the main sandbar and started our count; two of us calling out egg and chick numbers to a recorder, while the fourth person noted color bands on the adults. We all had to wear hard hats because the gulls get a little testy about people walking through their living room. The gulls in our immediate area would fly up over our heads making a terrific racket; so much so that we had to yell at the top of our voices to the recorder, who was only standing about ten feet away. Every once in a while I would feel a whack on top of the hard hat, as one of the gulls would become physically belligerent at my presence. Many of the eggs had already hatched and chicks were everywhere. A lot of them scurried away towards the water as we approached; some of them even swimming out from the land. They are born with big black webbed feet and seem to be able to swim quite well after hatching. Many of the eggs were still in the process of being pipped. We could see small holes in the eggs with pink tipped beaks sticking out. Some chicks were freshly hatched and lay in the nest with part of their body still inside half an egg shell and still wet from being inside the egg. It seems that the hatching of the eggs is staggered, as many nests contained both eggs and chicks. I didn't get the total count, but the colony certainly seems to be thriving. I wonder how big it will get before it stabilizes. In a couple of weeks they are going to go out to band the chicks, but I'll have to miss that, as I am going to leave Friday for Colorado and the ABA convention. Mike