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Mar.,1917 LIST OF BIRDS BRI?EDING IN SAN FRANCISCO COUNTY 57 larger waterfowl, which have non-breeding individuals remaining with us throughout the year. Loons are to be seen at Lake Merced throughout the en- tire summer; and seoters are apt to appear at any time of year on the ocean just off-shore. These are non-breeding birds, but we do not believe that this habit of re- maining for a season in their winter homes is to be found among the smaller birds. Neither xvould this rule apply to certain birds which evidently make San Francisco a feeding ground while nesting elsewhere. The Great Blue Heron, Black-crowned Night Heron and the Anthony Green Heron all come frequently into the Lake Merced region and less fre- quently to the Islais Marshes, but their nesting places are probably in San Mateo County or possibly in Alameda County. The American Bittern is a not-infrequent visitor to Lake Merced, but no man seems to be able to name its nesting place. Vultures and crows come over occasionally from Marin County, and it is a common experience on a summer evening to hear the hoarse croak of ravens overhead and to see these birds winging their way southward down Fig. 21. TULE-FRINGED SHORES OF LAKE MERCED, SA-?- FRANCISCO COUNTY. the coast. Gulls of several species are present through the summer, and in mid- summer the great run of the Dark-bodied Shearwaters is at its height just off- shore, and sometimes they pursue their finny prey into the bay. There are a few other birds the nesting of which within the county, while it cannot be affirmed, is not yet wholly beyond the limits of possibility. The Western Bluebird has been known to nest in the Mission District and may yet be found again nesting in the county. Eared Grebes are seen throughout the year on Lake Merced and it would not be surprising if they should sometime be found to nest there. Some kind of small owl has been shot occasionally by the park game wardens near the Prayer Book Cross. It is possible that they were Coast Screech Owls and that they nest somewhere in the county. The Dusky Horned Owl has been reported several times recently from Sutro Forest. We are indebted to Jesse Klapp, game warden in Golden Gate Park, for valuable assistance in our field work in the park. We have also gleaned a number of nesting records from Milton S. Ray's paper on the "Summer Birds of San Francisco County, California" (Condor xvm, 1916, p. 222). However,