Birds depend on their senses for survival, and bird senses have adapted to give birds the edge they need to thrive.
Understanding Bird Senses
Birds have the same senses humans do – sight, hearing, touch, taste and smell – but they are specialized to help birds survive. While a bird's exact senses depends on its species, all bird senses share certain characteristics.
A bird's eyesight is its most critical sense and the one it relies on the most for flight, evading predators and finding food. Birds have a thicker retina than humans and their eyes are larger in proportion to their head size. They have much denser rods and cones packed on the retina, giving them superior vision in both black-and-white and color. The range of colors birds see is not much greater than humans, but some species, such as hummingbirds, can see ultraviolet colors.
Where birds' eyesight really excels is in the perception of motion and detail – birds can see 2-3 times better than humans in that respect. In many birds, the eyes are positioned further apart on the head, giving them a wider field of view, and birds with eyes on the sides of their head – as most songbirds have – can nearly see directly behind themselves, which can be useful for detecting predators.
Because their vision is so critical, birds have a nictitating membrane (an inner eyelid) that helps protect their eyes and cleans them frequently. During a fight, birds often spread their wings to protect their eyes, and when attacking, they know instinctively to go for the eyes of the intruder.
Hearing is birds' second most important sense and their ears are funnel-shaped to focus sound. The ears are located slightly behind and below the eyes, and they are covered with soft feathers – the auriculars – for protection. The shape of a bird's head can also affect its hearing, such as owls, whose facial discs help direct sound toward their ears.
Birds hear a smaller frequency range than humans, but they have much more acute sound recognition skills. Birds are especially sensitive to pitch, tone and rhythm changes and use those variations to recognize other individual birds, even in a noisy flock. Birds also use different sounds, songs and calls in different situations, and recognizing the different noises is essential to determine if a call is warning of a predator, advertising a territorial claim or offering to share food.
Some birds, most notably oilbirds, also use echolocation, just as bats do. These birds live in caves and use their rapid chirps and clicks to navigate through dark caves where even sensitive vision may not be useful enough.
Birds do not use touch as extensively as humans, but it is still vital, particularly for flight. Birds are incredibly sensitive to changes in air temperature, pressure and wind speed, and those changes are transferred down the feathers to extensive nerves in the skin. Some birds have special feathers – rictal bristles – around the bill that may also serve a purpose for touch when feeding on insects or drumming into wood. Mutual preening is an important part of courtship behavior for many bird species, and it may be related to a sense of touch as well, since the birds are manipulating one another's feathers.
Birds have fewer nerves in their legs and feet, which makes them less sensitive to extreme cold and allows them to perch or stand on icy surfaces. Some birds have extremely sensitive touch receptors in their bills, which allows them to easily feed when probing through mud, water or other materials. This is particularly prominent in shorebirds and wading birds with long, specialized bills.
Birds do have a sense of taste, but it is not well refined. Depending on the species, birds may have fewer than 50 or up to roughly 500 taste buds, while humans have 9,000-10,000 taste buds. Birds can taste sweet, sour and bitter flavors, however, and they learn which of those tastes are the most suitable food sources. The sensitivity to different tastes varies by species, but most birds use other senses – sight and hearing most prominently – to locate the best foods.
Because of their unrefined tastes, when birds show a preference for certain foods, they're often relying on other factors. A bird may choose one food over another not because of taste, but because it is easier to acquire, there is less competition, their bills are better equipped for eating it or it has better nutrition for their dietary needs.
The sense of smell is the least developed sense for most birds. Most bird species have very small olfactory centers in their brains, and they do not use smell extensively. This debunks the myth that nesting birds will reject a fledgling that has been handled by humans – songbirds simply cannot detect the human scent.
There are some bird species, however, that have much better developed senses of smell. Vultures, kiwis, honeyguides, albatrosses, petrels and shearwaters all use smells to locate food sources and can often smell food from great distances, even when the odor may not be noticeable to humans.
Why Bird Senses Matter
By understanding bird senses, birders can learn about bird behavior and how to make the most of their birding in the field and in the backyard.
- Because birds see so well, it is important to wear appropriate clothing to go birding, including neutral colors. Adding a small bit of color to a backyard can also help attract birds.
- Because of birds' exceptional hearing, quiet pishing can be useful for finding birds, but loud, sudden noises can easily scare them away.
- It is important to never touch a wild bird, as a harsh hand could damage their touch receptors and hinder their flight.
- Clean bird feeders are essential since birds may not taste if the food has begun to spoil and may be dangerous.
- Choosing aromatic plants for landscaping will not attract birds; instead, plan bird-friendly landscaping with plants that double as food sources and safe shelters.
Birds have incredible senses, and understanding how they use those senses is a key step in helping them with survival and enjoying them at every level of birding.
Photo – Owl Eye © Hamed Saber