Uploaded November 2014 | Updated September 2026, 3 weeks ago
In some birds, feather colors may be created, or altered, by secretions from the urological gland, also called the preen gland. The yellow bill colors of many horn bills are produced by such secretions.
In some birds, feather colors may be created, or altered, by secretions from the urological gland, also called the preen gland. The yellow bill colors of many horn bills are produced by such secretions.
