Loon necropsies provide us with a good way to assess threats to the loon population.. Through these necropsies, we learned that lead poisoning is the leading cause of death for our loons. Each necropsy begins with an x- ray, followed by an internal exam of all the organs. This loon was found this summer on Stearns pond in Sweden Maine. Based on the initial x-ray, I thought this bird died from lead poisoning because I could see fishing gear in his gizzard. However, none of this fishing gear ended up being lead. With every necropsy, you start by examining the external features of the bird. We look for any external wounds, broken bones, dislocated joints, and external parasites. In the case of this bird, I found abrasions and bruising on his feet and around his left eye. He had no broken bones or dislocated joints and I found no external parasites.
Next, we examine the internal anatomy for any abnormalities. These include any discoloration, lesions, pre-mortem clots, parasites, organ enlargement or atropy and foreign bodies. This loon was in great body condition. He had plenty of fat and great muscle mass. One of the first abnormalities I noted was abdominal bruising on the lower part of his body. He also had a large pre-mortem clot on the underside of his sternum, as well as a lot of blood in his air sacs.
His organs, including his heart, lungs, liver and pancreas looked normal. The exception was his spleen, which was greatly enlarged. We confirmed his sex as well. Female loons only have a single ovary, whereas the males have two testes. Based on all the abnormalities found, we try and come up with cause of death. In this case, the bruising on his abdomen, combined with the large blood clot on his sternum and an enlarged spleen suggests blunt force trauma. While it is difficult to say exactly what caused his injuries, he could have been hit by a boat or even crash landed somewhere. If you find a dead or injured loon, please call our loon hotline: (207)-781- 6180 ext. 275.