What condition in birds is associated with a deficiency in vitamin D?

The correct answer is associated with rickets, a condition resulting from a deficiency in vitamin D. In birds, just as in mammals, vitamin D plays a critical role in the regulation of calcium and phosphorus, which are essential for proper bone development and maintenance. When birds do not have adequate vitamin D, they cannot adequately absorb calcium from their diet, leading to weakened bones and an increased risk of deformities and fractures—this condition directly corresponds with rickets.

Stargazing, while a term that may relate to certain neurological issues or behaviors in birds, is not caused by vitamin D deficiency. Instead, it is usually associated with other health issues such as lead poisoning. Frounce is a condition caused by a parasitic infection, particularly in birds of prey, and tapeworms are internal parasites that would lead to nutritional deficiencies but not specifically linked to a vitamin D deficiency. Consequently, rickets most accurately describes the health issue directly tied to a lack of vitamin D in birds.