Use of plumage and gular pouch color to evaluate condition of oil spill rehabilitated California brown pelicans (Pelecanus occidentalis californicus) post-release

Abstract

Sublethal effects of oil spills may dampen seabird rehabilitation success due to lingering negative impacts of contamination and stress on reproduction and long-term survival. These effects can be difficult to measure while birds are in care as well as once birds are released. Expression of sexually selected traits that are sensitive to condition can provide information on physiological status of birds. We evaluated plumage molt and gular pouch skin color of California brown pelicans ( Pelecanus occidentalis californicus) following oil contamination and rehabilitation to test for differences between previously oiled and rehabilitated (post-spill) and presumably uncontaminated pelicans. Post-spill pelicans released with either color leg bands alone, or bands plus harness-mounted satellite GPS tags, were relocated and visually assessed in the field at non-breeding communal roosts and compared to surrounding unmarked pelicans in the general population. Non-oiled pelicans bearing GPS tags were also included in the study. Post-spill pelicans lagged the general population in molt of ornamental yellow crown feathers but hind neck transition into white plumage was not significantly different. Both post-spill and non-oiled pelicans wearing GPS tags had lower gular redness scores than the unmarked, non-oiled population. Pre-breeding gular pouch redness of post-spill pelicans was more strongly influenced by wearing of a GPS tag than a history of oil contamination and rehabilitation. Gular pouch redness of post-spill pelicans in the first 18 months after release was positively correlated with long term survivorship. If gular pouch color is a condition-dependent sexual signal and overall health influences plumage molt progression, our results indicate that many post-spill pelicans marked with bands alone were in relatively good condition going into the next breeding season, but those released with electronic tags experienced additional stress due to wearing the equipment, introducing a confounding variable to the post-release study.

Postrelease Survival of California Brown Pelicans (Pelecanus Occidentalis Californicus) Following Oiling and Rehabilitation After the Refugio Oil Spill

“…One limitation of the study is the fact that these birds were outfitted with external harnesses and transmitters. Although we used tags well within the recommended range for weight, the presence of the tag and harness has the potential to impact energy balance; aero-and hydrodynamics; behavior; and stress level (Warnock and Takekawa 2003;Vandenabeele et al 2011;Jaques et al 2019). The long-term survival of some birds despite the instrumentation, however, suggests that the tags were well tolerated.…”

Estimating the numbers of aquatic birds affected by oil spills: pre-planning, response, and post-incident considerations

“…(2) focused only on expression of molecular markers associated with hydrocarbon exposure (e.g., Trust et al 2000;Pérez et al 2008Pérez et al , 2010Franci et al 2014;Paruk et al 2014;Nisbet et al 2015;Fallon et al 2018); or (3) examined rehabilitated individuals released back into the wild (e.g., Fowler et al 1995;Chilvers et al 2015;Jaques et al 2019).…”

Effects of pollution on marine organisms

“…Other researchers documented adverse impacts to birds from oiling and rehabilitation beyond survivorship. In San Francisco Bay, California brown pelicans (Pelecanus occidentalis californicus) oiled by the Cosco Busan 2007ANNUAL LITERATURE REVIEW IFO-380 heavy fuel oil spill in San Francisco Bay, and rehabilitated transitioned to breeding plumage (yellow crown feathers) significantly slower and had less intense gular coloration than nonoiled, nonrehabilitated birds (Jaques, Mills, Selby, Veit, & Ziccardi, 2019). Interestingly, the presence of Global Positioning System (GPS) transmitters on brown pelicans, regardless of oiling and rehabilitation status, resulted in similar adverse impacts.…”