How long do rehabilitated oiled animals survive after release, and do they return to normal biological function? Post-release survival is a critical knowledge gap in understanding the overall effects of oil in wildlife.
Several reports in the scientific literature suggest that oiled and rehabilitated animals survive for only days, not months or years. Other reports show examples of birds surviving decades after being cared for during an oil spill event. However, relatively few large-scale scientific studies have been undertaken to define the success of oiled wildlife rehabilitation efforts.
To address this lack of information, the OWCN has conducted specific studies on the post-release survival of rehabilitated oiled wildlife since 1995. When possible, OWCN conducts such projects on every spill in California.
Post-release studies are collaborative efforts between the OWCN and appropriate experts, with funding coming from a reserve within the OWCN budget. This research is crucial not only to determine that treated animals survive and return to normal after release, but also that protocols are improved based upon the success of the animals in their natural environment.
Overview of Studies
To date, several post-release projects on oiled seabirds have been initiated by the OWCN:
- 1995: Following American coots following a crude oil spill in Long Beach
- 1997: Evaluating Western gulls after the Torch/Platform Irene spill off the central coast
- 1999: Evaluating common murres after the Stuyvesant oil spill in northern California
- 2007: Tracking surf scoters affected during the Cosco Busan oil spill in San Francisco
- 2015: Following brown pelicans after the Refugio oil spill off of Santa Barbara
Each project used tracking devices attached to rehabilitated and control birds and followed animals after release.
In addition to these intensive studies, all birds released after an oil spill are individually identified with a federal leg band. This enables others to report sightings of rehabilitated birds in the wild.
In 2017, the OWCN and OSPR published a compilation of post-release information detailing the successes of oiled wildlife collection and care, and addressed the ongoing questions of whether oiled wildlife response is “worth it”
- Henkel LA, Ziccardi MH. 2017. Life and Death: How Should We Respond to Oiled Wildlife?. Journal of Fish and Wildlife Management, 9(1):296-301.
Results of Studies
In each study, findings suggested that overall success (as determined by survival) was better than previously thought – largely due to the development of the OWCN and other spill response organizations around the world.
- Anderson DW, Newman SH, Kelly PR, Herzog SK, Lewis KP. 2000. An experimental soft-release of oil-spill rehabilitated American coots (Fulica americana): I. Lingering effects on survival, condition and behavior. Environmental Pollution. 107(3):285-94.
- Newman SH, Anderson DW, Ziccardi MH, Trupkiewicz JG, Tseng FS, Christopher MM, Zinkl JG. 2000. An experimental soft-release of oil-spill rehabilitated American coots (Fulica americana): II. Effects on health and blood parameters. Environmental Pollution, 107(3):295-304.
- Golightly RT, Newman SH, Craig EN, Carter HR and Mazet JAK. 2002. Survival and behavior of Western Gulls following exposure to oil and rehabilitation. Wildlife Society Bulletin 30(2): 539-546.
- Newman SH, Golightly RT, Craig EN, Carter HR and Kreuder C. 2004. The effects of petroleum exposure and rehabilitation on post-release survival, behavior and blood indices: A Common Murre (Uria aalge) case study following the Stuyvesant petroleum spill. OWCN Final Report.
- De La Cruz SE, Takekawa JY, Spragens KA, Yee J, Golightly RT, Massey G, Henkel LA, Larsen RS, Ziccardi MH. 2013. Post-release survival of surf scoters following an oil spill: an experimental approach to evaluating rehabilitation success. Marine Pollution Bulletin, 67(1-2), pp.100-106.
- Lamb JS, Fiorello CV, Satgé YG, Mills K, Ziccardi M and Jodice PGR. 2018. Movement patterns of California brown pelicans (Pelecanus occidentalis californicus) following oiling and rehabilitation. Marine Pollution Bulletin, 131, pp.22-31.
- Lamb JS, Satgé YG, Fiorello CV, Jodice PG. 2017. Behavioral and reproductive effects of bird-borne data logger attachment on Brown Pelicans (Pelecanus occidentalis) on three temporal scales. Journal of Ornithology, 158(2):617-27.
- Jaques DL, Mills KL, Selby BG, Veit RR, Ziccardi MH (2019) Use of plumage and gular pouch color to evaluate condition of oil spill rehabilitated California brown pelicans (Pelecanus occidentalis californicus) post-release. PLoS ONE 14(2): e0211932. https://doi.org/10.1371/journal.pone.0211932
- Mills KL, Gaydos JK, Fiorello CV, Whitmer ER, De La Cruz S, Mulcahy DM, Vilchis LI, Ziccardi MH. 2016. "Post-Release Survival and Movement of Western Grebes (Aechmophorus occidentalis) Implanted with Intracoelomic Satellite Transmitters," Waterbirds, 39(2), 175-186.