By John M. Coluccy, Ph.D.
Ducks and geese have the same five senses that people do. But in waterfowl these abilities are highly adapted to the environments in which the birds live. Read along as we explore the acuity and utility of the five senses in waterfowl, and how these faculties help ensure the birds' survival throughout their amazing annual journeys.
Whether in the air or on the marsh, waterfowl rely more on sight than any other sense. The structure of the eye in waterfowl allows the birds to see objects in fine detail two and a half to three times farther away than humans can. Ducks and geese can also see a much broader spectrum of colors—spanning from near-ultraviolet to red—than people do.
Because their eyes are located on the sides of their head, waterfowl have panoramic vision, which enables them to see almost everything around them at once. However, this ability comes at a price—reduced depth perception. Waterfowl compensate by moving their head rapidly from side to side, allowing the birds to observe an object with one eye from two different angles in quick succession, which creates a three-dimensional picture.
The ability of waterfowl to recognize visual cues is important in almost every aspect of their lives, from finding their way around a marsh to navigating great distances between breeding, staging, and wintering areas. Their acute vision also aids in detecting potential danger from predators, including hunters. Just think how many times waterfowl have flared out of range while you were hunting because of movement in the blind or the glint of a shotgun barrel.
Keen vision is also extremely important to some waterfowl species while foraging. Sight feeders such as mergansers, which pursue mobile prey underwater, are a prime example. Their eyes are placed farther forward on their head than they are on other waterfowl, which helps them target minnows and other fast-swimming aquatic animals.
After sight, hearing is perhaps the second most important sense to ducks and geese. Waterfowl ears lack external appendages and are located slightly behind and below the eyes. The ear openings are covered with soft feathers, called auriculars, which offer protection and help muffle the sound of the wind when the birds are in flight.
Waterfowl use a variety of vocalizations, such as mating and alarm calls, to communicate with each other, and the birds' ability to differentiate between these calls is crucial to their survival. Waterfowl rely on their hearing to maintain contact with mates and young, even in noisy flocks. Hearing may be used by diving waterfowl to locate food. While still in the egg, waterfowl embryos learn to recognize the sound of their mother's voice through a process known as imprinting. They also communicate with other members of the brood to synchronize their development. This ensures that all the ducklings will hatch at almost the same time and be ready to respond to their mother's calls when it's time to leave the nest, usually within 24 hours of hatching.
The sense of touch helps waterfowl distinguish among a variety of physical stimuli, including temperature, pressure, and texture. Touch is especially important to waterfowl while they are foraging. Many waterfowl species are tactile feeders and use their bills to search for food in murky water and along the bottom of wetlands, where their vision is rendered useless. Highly sensitive nerve endings called Herbst corpuscles are located in a series of pits running along the tip of the bill. These touch receptors allow species like canvasbacks to find succulent wild celery tubers and other soft foods while probing the substrate of wetlands. Conversely, waterfowl have fewer nerves in their feet, making these appendages less sensitive to cold, which enables them to stand on snow or ice for extended periods of time.
The sense of taste in waterfowl is generally considered to be less well-developed than that of mammals and many other animals. Taste is a sensation produced when food particles in the mouth react chemically with receptor cells located on the taste buds, which are typically located in greatest number on the tongue. Generally speaking, the more taste buds you have, the better your sense of taste. Waterfowl have only about 400 taste buds, while humans have 9,000 and catfish have a whopping 100,000. Nevertheless, the presence of small numbers of taste buds indicates that waterfowl have at least some capacity to distinguish between certain flavors. In fact, chemical repellents have recently been developed to keep resident Canada geese away from crops and lawns. When applied, these chemicals, which come in flavors such as grape soda, have been shown to render crops and grass unpalatable to Canada geese.
For a long time, the sense of smell in waterfowl was thought to be the least developed of their senses. Although their olfactory systems may not be as keen as those of dogs or even some other birds, waterfowl can detect smells to varying degrees. Research suggests that greylag geese can distinguish between food plants and other vegetation via their sense of smell. In addition, uropygial gland secretions in domestic ducks have been shown to serve as pheromones for mating and to aid in species recognition.
Whether it's a wood duck navigating through interlacing tree branches at breakneck speed, a blue-winged teal migrating from the Prairie Pothole Region to the Caribbean, or a long-tailed duck diving in deep coastal waters to find a mussel bed, waterfowl rely on their five senses to thrive in varied environments. The next time you have an opportunity to observe waterfowl in nature, consider how these amazing birds perceive the world through their abilities to see, hear, touch, taste, and smell.
Dr. John Coluccy is director of conservation planning in DU's Great Lakes/Atlantic Region.