The absence of external ear flaps, or pinnae, often leads to the mistaken idea that ducks do not possess ears. Ducks and all other birds rely on a highly specialized auditory system concealed beneath their plumage. This hidden structure allows them to process sounds in both terrestrial and aquatic environments.
The Hidden Location of Duck Ears
A duck’s ear is located on the side of its head, slightly behind and below the eye, marked by a small opening called the external auditory meatus. This opening is completely covered by a patch of specialized feathers known as auriculars or ear coverts. These feathers serve a dual purpose, acting as both protection and an acoustic aid.
The auricular feathers shield the delicate inner ear structures from wind, debris, and water intrusion. They also function as a natural baffle, channeling sound waves toward the ear opening. For diving ducks, this covering prevents water from entering the ear canal when they submerge, allowing them to retain hearing sensitivity.
Anatomy of the Avian Ear
Like mammals, the avian ear consists of external, middle, and inner sections, but the internal components show distinct evolutionary differences. The external auditory meatus leads to the tympanic membrane, or eardrum, which separates the outer ear from the air-filled middle ear cavity. Unlike the inwardly bulging mammalian eardrum, the duck’s tympanic membrane bulges slightly outward.
The middle ear contains a single bone, the columella, which transmits sound vibrations from the eardrum to the inner ear. This single ossicle contrasts with the three small bones found in the mammalian middle ear. The inner ear contains the cochlea, which is shorter and less coiled than the mammalian equivalent, where sensory hair cells convert vibrations into electrical signals the brain can interpret.
How Ducks Process Sound
Ducks possess excellent hearing, especially within the mid-frequency range, which is important for detecting environmental sounds and communication. In-air hearing sensitivity for ducks is greatest between 1,000 and 3,000 Hertz (Hz), a range that encompasses many of their vocalizations. Specific sea duck species, such as the long-tailed duck, show peak underwater hearing sensitivity between 1 and 3 kilohertz (kHz).
The lack of a prominent external pinna presents a challenge for sound localization, particularly in determining the vertical origin of a sound. Ducks compensate for this by using their entire head shape, which absorbs and diffracts sound waves to create subtle volume differences between the two ear canals. The avian brain uses these minute differences in timing and intensity to construct a precise map of the sound source, allowing them to pinpoint the location of a predator or a mate’s call.