Impacts to birds from marine oil spills in California, 1995–2019

We compiled data on marine and coastal petroleum oil spills in California during 1995-2019 that affected ≥10 birds (n = 30). These spills resulted in the collection of 12,842 birds (5241 collected alive, 7601 collected dead). Frequency of spills decreased over the study period, and varied intra-annually, with more spills and more birds collected during fall and winter months. The greatest number of spills affecting birds were in southern California (19/30), although far more birds were collected from spills in northern California (11,570/12,842). Most spills in southern California were related to oil production or pipeline transport, whereas most spills in northern California (and most impacted wildlife) were related to non-tank vessel spills. The most abundant bird species affected were Common Murre (Uria aalge), Western or Clark's Grebe (Aechmophorus occidentalis/clarkii), and Surf Scoter (Melanitta perspicillata). Species-specific injury rates were roughly in proportion to species' abundance in the spill area and the amount of time they spend on the surface of the water. Some species were collected more often live than dead and these species also tended to have higher release rates. This information on geographic, temporal, and species-specific risk to birds from oil spills can be used to inform effective prevention and response measures for oil spills in California and elsewhere.