Abstract
Given recent concern over the effects of dioxin on wildlife, we collected 33 Great Cormorant Phalacrocorax carbo shot along the Yahagi River, Aichi Prefecture, during the period from March to June 2005. Quantitative histological assessments of their thyroid glands revealed that the majority (93.9%) had hyperplastic glands. We suggest that this hyperplasia may be associated with their main diet of fish, which could be contaminated with dioxin.
