Jan.,1918 DESTRUCTION OF BIRDS AT LIGHTHOUSES, CALIFORNIA COAST The returns seem to indicate that the danger to birds increases in direct proportion to the distance of the lighthouse lantern above the ground, while the general elevation of the whole structure is also an important factor. Many of the lighthouses are situated near sea level and at the foot of high bluffs, and not one so situated reports any bird destruction. But where the lighthouse is located on a height, even though it be not very high itself, there is considerable Fig. 2. Lighthouse at Point Arena, Mendocino County, Cali- fornia. The "brick chimney" type, whose great height makes it dangerous to birds. The light at this station is 155 feet above the sea, and the keeper reports from ten to thirty birds per night killed on calm, dark nights during the migration seasons. Courtesy of the Lighthouse Service. U.S. Dept. Commerce. mortality. This is indicated by the fact that the average elevation of all the lighthouses reporting birds killed is 165 feet, while the average elevation of all the lighthouses reporting no birds killed is only eighty-eight feet. III. The larger birds are killed by flying. violently against the glass or other portions of the lighthouse structure; small birds are also sometimes killed in this way, but sometimes also they become confused, and fly about and
