Abstract

The Wildlife Conservation Society has performed health assessments on the common loon (Gavia immer) in New York state’s Adirondack Park since 2003 in conjunction with a multi-institutional, long-term banding and mercury project. Sixty loons (28 males, 25 females, 7 unsexed juveniles) have been evaluated. Not all testing was performed on all birds. Serum was evaluated for exposure to avian viruses (avian influenza [n=48], adenovirus [n=48], infectious bursal disease [n=40], avian encephalitis [n=47], avian reovirus [n=40], paramyxovirus 1 [Newcastle disease virus] [n=48]), paramyxovirus 2 [n=40], paramyxovirus 3 [n=40], and infectious laryngotracheitis [n=37]); pesticides (aldrin [n=47], benzene hexachloride [BHC] [n=47]), endosulfane (n=32), chlordane (n=32), dichlorodiphenyldichloroethane [DDD] [n=47], dichlorodiphenyldichloroethylene [DDE] [n=47], dichlorodiphenyltrichloroethane [DDT] [n=47]), dieldrin [n=47], endrin [n=44], heptachlor [n=47], nonachlor [n=44], polychlorinated biphenyls [PCBs] [n=46]); and heavy metals (lead [n=48], zinc [n=12], arsenic [n=48], cadmium [n=48], thallium [n=48], mercury [n=40]). Complete blood counts, serum biochemistries (n=30), and fecal endoparasite evaluations (n=13) were also performed.

The results demonstrate that 20% of the loons were exposed to avian influenza (typing not performed), and a small percentage of birds were exposed to avian encephalitis (2%) and paramyxovirus 1 (9%). There was very little exposure to other avian viruses, with no serologic evidence of adenovirus, infectious bursal disease, avian reovirus, paramyxovirus 2, paramyxovirus 3, or infectious laryngotracheitis. There was evidence of ongoing exposure to metabolites of pesticides that have been banned for decades (Table 1). There was no exposure to aldrin, BHC, endosulfane, chlordane, endrin, or heptachlor. Two adult loons had low lead levels, while one juvenile had a lead level (12.3 ppm) that may have been high enough to affect the animal’s behavior. Mercury levels were high enough in some of the study birds to impact their reproductive success. Fecals were performed on 13 animals, 61% had trematodes, 23% had Eimeria sp., 15% had both parasites, and 31% of the loons were negative. Complete blood counts were similar to those published,¹ although the heterophil percentages were higher and eosinophil percentages were lower than published values. There are no published reports of serum biochemistries in loons but when compared to plasma biochemistries of another piscivorous bird, flightless cormorants (Phalacrocorax harrisi),² loons had lower aspartate transferase, total protein, and albumin and higher levels for glucose, chloride, and uric acid. Both species had similar values for globulins, calcium, and sodium.

Table 1. Results of pesticide and heavy metal testing in
common loons in the Adirondack State Park from 2003-2008

^aDDT-dichlorodiphenyltrichloroethane
^bDDE-dichlorodiphenyldichloroethylene
^cDDD-dichlorodiphenyldichloroethane
^dPCBs-polychlorinated biphenals

Acknowledgments

The authors thank the Global Health Program veterinary technicians and High Peaks Animal Hospital for their assistance with this project.

Literature Cited

1.  Haefele HJ, Sidor I, Evers DC, Hoyt DE, Pokras MA. Hematologic and physiologic reference ranges for free-ranging adult and young common loons (Gavia immer). J Zoo Wildl Med. 2005;36:385–390.

2.  Travis EK, Vargas FH, Merkel J, Gottdenker N, Miller RE, Parker PG. Hematology, plasma chemistry, and serology of the flightless cormorant (Phalacrocorax harrisi) in the Galapagos Islands, Ecuador. J Wildl Dis. 2006;42:133–141.