Nutritional secondary hyperparathyroidism in free-living fledgling American crows (Corvus brachyrhynchos brachyrhynchos).

From June 1994 to June 1996, 18 fledgling American crows (Corvus brachyrhynchos brachyrhynchos) from multiple locations on Long Island, New York, were presented with signs of metabolic bone disease characterized by folding fractures of the proximal tibiotarsus. Plasma alkaline phosphatase levels were elevated, and the calcium/phosphorus ratio and 25-hydroxycholecalciferol (25-(OH)D3) levels were decreased. The histopathologic diagnosis was parathyroid hyperplasia and generalized osteodystrophia fibrosa. A diet low in bioavailable calcium and/or vitamin D3 was the probable cause. Also, exposure to xenobiotics could have contributed to the depression of 25-(OH)D3 levels.