Abstract

Birds that live in a marine environment have developed specialized mechanisms to cope with their saline surroundings. Short–term and long-term physiologic changes along with evolutionary adaptations in the gastrointestinal tract, salt glands, and kidneys are necessary to survive in this environment.^1,2 Because seawater is often impractical or expensive to use at wildlife rehabilitation centers, freshwater is often used to house these animals. We hypothesized that housing pelagic birds on freshwater for days or weeks while undergoing rehabilitation can cause physiological stress and can impact their electrolyte levels. To investigate the impacts of fluid therapy and housing, three species of seabirds, common Murres (Uria aalge), Western grebes (Aechmophorus occidentalis), and Northern fulmars (Fulmarus glacialis), were monitored during rehabilitation at the San Francisco Bay Oiled Wildlife Care and Education Center following stranding events in 2009 and 2010. Birds were gavaged with freshwater or a hypertonic saline solution, and housed on freshwater throughout the rehabilitation process. During the course of rehabilitation, we collected blood for serum chemistries at intervals between 1 and 6 days following administration of fluids. Common Murre and Northern fulmar sodium and chloride levels were found to be significantly lower than those of comparable wild populations, while electrolyte concentrations in Western grebes (a bird that spends time in fresh and saltwater environments) did not differ significantly from wild counterparts. Our study suggests that the use of freshwater for pelagic birds may cause physiological stress in birds that live solely in a pelagic environment with the potential for decreased likelihood of a positive outcome.

Acknowledgements

The authors wish to thank Michelle Belizzi, Marie Travers and all the staff and volunteers of the International Bird Rescue Research Center, Cordelia, CA, for technical assistance, and the Oiled Wildlife Care Network, Davis, CA for financial and logistical support of this project.

References

1.  Holmes WN, Phillips JG. The avian salt gland. Biological Reviews 1985; 60(2): 213–256.

2.  Hughes MR. Regulation of salt gland, gut and kidney interactions. Comparative Biochemistry and Physiology Part A 2003; 136: 507–524.