Fulica americana -130- Lake Temescal, 420ft, Alameda Co., Calif. silence. One of the platform structures examined today seemed to consist of an old nest structure with a great of excrement piled on top like mud. One bird was in close, apparently a little concerned over my presence - A few minutes later a ? + ? Cooper Hawk flew into a tree about 1/2 way down the W side of the lake. They seemed to be engaging in some sort of a display - very soon a group of mallards and coots collected in the water nearly, raising a considerable fuss. The ? hawk made one pass at the water-fowl, they scattered but quickly collected again. The ? hawk crossed the lake, the birds didn't respond, the ? + crossed the lake, swinging low, and causing about 6 nearly coots to duck under water. Once a coot persistently chased a Buffle Duck out on the open water, the duck finally flew to escape - but I haven't seen a coot chasing a mallard yet. I noticed today in connection with display behavior, that the birds flatten the feathers on the top of their head and elevate the neck feathers, giving their necks an expanded appearance, while the depression of the crown feathers accentuates the prominence of the frontal shield - giving them this sort of a profile.