What is the condition known as "frounce" characterized by?

Frounce is a condition primarily characterized by yellowish growths that develop in the mouth and throat of birds, particularly in raptors. This condition is caused by a parasitic infection from a protozoan called Trichomonas gallinae, which often affects the digestive system and can lead to significant health issues if not addressed. The yellowish lesions can obstruct the bird's feeding and cause pain and discomfort, making it essential for falconers and bird caretakers to recognize and treat this condition promptly.

The other options address different health issues that can affect birds but are not related to the symptoms of frounce. Abnormal feather loss pertains to conditions like molting or feather disease, while difficulty in flight could stem from various causes, including injuries or other health problems. Swelling in the legs might indicate conditions unrelated to frounce, such as infection or other systemic issues. Recognizing the specific symptoms of frounce is crucial for effective diagnosis and treatment.