The Swainson’s Hawk (Buteo swainsoni) was once a common raptor inhabiting eastern San Luis Obispo County (Louis Silveria pers. comm., Fred Truesdale field notes). It is now an uncommon breeding species throughout California and nesting in San Luis Obispo County is extremely rare. I attempted to locate Swainson’s Hawk nesting territories during spring 1977 while conducting other research in the Coast Ranges of California.
A pair of Swainson’s Hawks was reported to nest in 1976 on the San Juan Creek, San Luis Obispo County (Ron Walker pers. comm.). The nest was occupied in 1977 by Red-tailed Hawks (Buteo jamaicensis) (Lynette Shirley pers. comm.). I observed this nesting territory in 1977. It consisted of a large, isolated, dead cottonwood (Populus sp.) in the dry floodplain of San Juan Creek which runs through oak woodland, grassland and agricultural plant communities. The nest was placed on one of the few remaining large horizontal branches of the tree. It appeared that the nesting Red-tailed Hawks had added fresh sticks to the bulky stick nest.