Interactive mortality factors in common loons from Maritime Canada

Area of Science:

• Wildlife toxicology
• Avian pathology
• Environmental health

Background:

• Common loons (Gavia immer) are sensitive indicators of aquatic ecosystem health.
• Previous studies have identified various threats to common loon populations, including environmental contaminants and disease.

Purpose of the Study:

• To investigate the health status and potential causes of mortality in common loons from the Maritime provinces of Canada.
• To determine associations between body condition and specific pathological findings in necropsied loons.

Main Methods:

• Necropsy of 31 common loons found between August 1992 and November 1995.
• Assessment of body condition, and examination for lead poisoning, respiratory mycosis, oil contamination, intestinal parasites, and renal mercury levels.

Main Results:

• Eight loons were in good condition with acute causes of death (drowning, trauma).
• Twenty-three loons were in poor condition, with common findings including chronic lead poisoning, respiratory mycosis, oil contamination, higher parasite loads, and elevated renal mercury levels.
• Poor body condition was significantly associated with higher numbers of intestinal trematodes and renal mercury levels.

Conclusions:

• Multiple concurrent disease processes, including environmental contaminant exposure and parasitism, are associated with poor body condition and likely contribute to mortality in common loons.
• Environmental factors and disease agents may act synergistically to impact wildlife health.
• This study underscores the complex interplay of factors affecting wild animal health and survival.