Bird Island - Bird Island sits offshore of the Marin Headlands just south of Rodeo Beach. The rock consists of gray basalt (or diabase) of the Franciscan Complex with a whitewash coating of bird guano. Tennessee Point sticks out beyond the sandstone cliffs just north of Rodeo Beach, which can be seen in the background, at the far right. Point Reyes is the peninsula in the distance. For a simplified geologic map of the Marin Headlands, see NPS, [2010].