POST-RELEASE MONITORING OF OILED BROWN PELICANS FROM THE 2015 REFUGIO OIL SPILL

Abstract

ABSTRACT A great deal of effort and resources is expended on the cleaning and rehabilitation of oiled wildlife, but the ultimate fate of these animals is often unknown. Post-release monitoring is essential for improving methodology and directing resources to those animals most likely to survive after release. The Refugio oil spill occurred in May 2015, spilling approximately 100,000 gallons of oil on the California coast near Santa Barbara. Brown pelicans were the most common avian species affected. We instrumented 12 oiled pelicans with solar-powered satellite GPS tags at the time of their release following cleaning and rehabilitation. An additional 8 control (unoiled) pelicans from a nearby area were similarly instrumented and released immediately. All birds survived for at least 12 weeks. In the first 6 months after release, distance traveled and movements were similar between rehabilitated and control pelicans. Several individuals traveled >5000 km, migrating to northern California or central Oregon in the late summer and early fall. In the spring, most birds traveled south, some as far as southern Baja California. Mortality was documented among both rehabilitated and control birds; however, the majority of birds that stopped transmitting were never found. Lack of transmission could represent mortality, tag or battery failure, or tag loss. After at least 40 weeks of tracking, 5 birds (3 rehabilitated and 2 control) were still transmitting. Based on presence in breeding colonies, none of the birds appeared to breed. These results demonstrate that brown pelicans can survive and travel long distances following oiling and rehabilitation.