Photograph of nests of Mud Martins found in the granite rock approximately thirty feet high in San Luis Obispo County, August 1938. The tall rock seems to lean to the left with a sloping, grassy field below. The nests look like hundreds of tiny caves made on the side of the rock and they are generally clustered together. "Nests of the Mud Martins found in the granite rock approximately thirty feet high. These nests found on Swallow Rock in San Luis Obispo County. Piedra de las Golondrinas or Swallow Rock, a famous old time landmark, at west side of Morro Cayucos road. Mud Martinis have nested on this rock as far back as history goes. Granite up thrust about 30 feet. Photo August 1938. Elevation (ground) 130'. Located at mouth of Green Valley and opposite site of Jose Ramon Estrada adobe (no longer present), 3 miles south of town of Cambria (or Cambia?). Estrada owned Rancho Santa Rosa, which later became part of Hearsts' holdings. Cambria is on Ranco Santa Rosa".