Sensory Perception in Birds

Have you ever stopped to think about the incredible diversity in bird lifestyles? No matter which country you live in, you can find birds living in practically every habitat and capitalizing on any available food resource. The secret to their success? Six amazing senses.

Whether they’re looking for food, charming a potential partner, dodging a predator, or navigating on migration, birds rely on their senses to interpret the world around them. However, a flightless Penguin in the Southern Ocean has different sensory needs to a songbird in a suburban back yard, so we see plenty of variation in the sensory organs and abilities of birds across the globe.

In this guide, we’ll dive into the avian senses and learn how birds perceive the world. Read along to learn all about sensory perception in birds.

Vision

Eye Structure and Function

Birds rely on their vision more than any other sense. Their eyes are large and located either on the sides of the head for a wide field of view (predator detection) or toward the front of the face for binocular vision (prey detection).

The avian eye is comparable to our own, although there are a few differences. Birds have a ring of bone around their iris (sclerotic ring) and a unique structure at the back of the eye called the pecten oculi, which is believed to supply nutrients and blood to the retina. Like many other animals, birds have a ‘third eyelid’ called a nictitating membrane that sweeps horizontally across the eye to keep its surface moist and clean.

Color Vision and UV Perception

Most birds are diurnal, with densely packed cones on the retina for excellent color vision. Remarkably, many birds are known to have tetrachromatic vision, which means they have four types of color-sensitive cones and can detect light in the ultraviolet (UV) spectrum.

Ultra-violet vision is thought to help them find food and see details on their plumage invisible to the human eye. It’s likely that many birds look very different when seen through the avian eye, and some species may have many more colors than we can perceive.

Adaptations for Hunting and Foraging

Most birds detect their food by vision, and some have special adaptations to improve their success. The birds of prey have large, powerful eyes dominated by color-sensitive cones, providing especially acute long-distance vision for spotting their prey and estimating its distance.

In contrast, nocturnal birds have rod-dominated retinas for detecting their prey in low light. The tube-shaped eyes of Owls are especially well-developed and often have a reflective tapetum lucidum at the back that passes light back through the retina.

Want to learn more about some amazing avian vision adaptations? Check out this fact-filled guide!

Like many other animals, birds have a ‘third eyelid’ called a nictitating membrane that sweeps horizontally across the eye to keep its surface moist and clean. Common Grackle

Hearing

Auditory Structure

Birds may not have external ears, but they certainly can hear. The ears are located behind and below each eye, although they’re typically covered in specialized auricular feathers and barely visible. Structurally, they consist of an outer, middle, and inner section.

The inner parts of the avian ear are separated from the outside world by a tympanic membrane (ear drum), which is in contact with a single middle ear bone called the columella.

Vibrations are transmitted through this structure to the cochlea and then onto the auditory nerve, which communicates with the brain. Birds also have a special organ in their ear that helps them detect air pressure variations that signal weather changes.

Song Recognition and Communication

Birds communicate primarily through sound. Songbirds sing to defend their territories or attract a mate, but most birds also produce a range of calls to express excitement, aggression, alarm, and other important information.

Naturally, birds need good hearing to detect these forms of auditory communication and to recognize and analyze the sounds in context. They can hear a relatively limited range of frequencies compared to humans, although they have much ‘faster’ hearing than we do, allowing them to hear brief notes and details in complex songs.

Environmental Sound Interpretation

Hearing isn’t only useful for communicating with other birds. Avians also rely on hearing to detect sounds like the rustling of a rodent in grass or an insect moving through the leaf litter. Birds also listen out for sounds of danger, like the approach of a predator or the sound of a snapping branch above them.

Tactile Sensations

Feather Sensitivity

Feathers themselves have no nerves, but that doesn’t mean these specialized structures aren’t useful for tactile perception. Many birds have special feathers on their head and around their bills that work in a similar way to the whiskers of a mammal. These touch-sensitive feathers may help birds navigate in the dark, detect prey, or protect their faces from injury.

Birds also have special feathers called filoplumes with touch receptors near their follicles. These bristle-like feathers anchor near their flight feathers and allow birds to monitor their position. This is important when preening, adjusting the position of their feathers, moving their feathers before defecating, and controlling their feather position in flight.

Beak and Skin Sensitivity

The skin and the beak are the most important tools for tactile perception because these are the body parts that typically come into contact with objects in the world around them. Birds can detect temperature, pressure, pain, and touch with their skin and feet, although their lower limbs are covered in a tough, scaly skin called the podotheca.

Some birds use their bills to detect food particles or prey, and these species may have extra-sensitive bills. Shorebirds that probe for invertebrates in the mud and waterfowl that filter food from the water have particularly tactile beaks.

Many birds have special feathers on their head and around their bills that work in a similar way to the whiskers of a mammal. Kiwi foraging in natural habitat

Taste and Smell

Taste Buds and Preferences

Birds don’t have the best sense of taste in the animal kingdom, but they certainly do have tastebuds. Most species can taste four of the five taste groups, i.e., salty, sour, umami, and bitter, although some can also detect sweet flavors.

Birds use their tastebuds to determine the quality and safety of the food they eat. They may show preferences for some foods based on their energy content (e.g., carbohydrates in nectar) and reject others based on toxicity (e.g., insects with chemical defenses).

Olfactory Abilities

Like taste, smell is a relatively weakly developed avian sense, although it is essential for some species. Let’s take a look at some interesting examples:

• Turkey Vultures have a relatively well-developed sense of smell for detecting animal carcasses.
• Leach’s Storm Petrels can locate their nest sites in the dark by smell.
• White Storks can smell freshly mown fields where food is easy to find. They may come in from several miles away to forage for exposed prey items.
• Hummingbirds can smell the formic acid produced by ants and may use their sense of smell to avoid competition at nectar sources.

Magnetoreception

Magnetic Sensitivity

A little over 50 years ago, scientists studying European Robins proved that birds can detect magnetic fields. The mechanisms of this avian ‘superpower’ are complex (think quantum mechanics!), but they involve special cells in the retina that allow birds to ‘see’ the Earth’s magnetic fields in daylight.

Role in Migration and Homing

So why would birds need to see magnetic fields? Knowing where the poles and the equator are can help birds navigate the world. This information could help them find their way back to the nest after a long foraging trip or help migratory species return to nesting grounds thousands of miles away each spring.

Want to learn more about how birds find their way? Check out our in-depth guide to bird navigation!

Turkey Vultures have a relatively well-developed sense of smell for detecting animal carcasses

Integrating Sensory Information

Neurological Processing

As we’ve learned, birds have six extraordinary senses for gathering information about their surroundings. However, sensory information is useless without a way to process it into meaningful data that triggers reflexes or informs conscious decisions.

These tasks are performed by the central nervous system, which consists of a spinal cord and a well-developed brain. Combined, the information processed in the brain facilitates spatial awareness through an integrated, multisensory experience in every waking moment.

Behavioral Responses

The information gathered by sensory organs must be translated into actions or behaviors if the individual is to benefit from their senses. Almost every action birds perform is driven by this kind of information. For example, a flying bird will use its vision to spot obstacles in its path and the filoplume feathers in its tail to adjust its rectrices (tail feathers) to alter its course.

Let’s consider a few other typical bird behaviors and the senses birds use to guide them.

• Migration - Birds use their keen vision to guide their path by day or night. Some birds use magnetoreception and even smell for navigation.
• Foraging - Most birds look for their prey, but some use smell, touch, and hearing to locate their food.
• Communication - Birds rely on hearing to communicate through songs and calls. However, unique plumage patterns, colors, and courtship displays are all forms of visual communication that depend on avian eyesight.
• Predator detection - Birds are extremely vigilant and rely on sharp, ‘fast’ vision to detect threats in time to flee. Hearing is also crucial for detecting sounds like the stalking footprints of an approaching cat.

Birds rely on hearing to communicate through songs and calls. Bluethroat in song

Summary

There’s a reason birds are so successful across habitats across the globe. Their superior senses help them navigate, find the sustenance they need, and stay out of trouble. There’s still much to learn, of course, but science continues to uncover exciting discoveries about the way birds perceive their environment.

Unfortunately, sharp senses aren’t always enough, especially in our changing modern world. ‘New’ threats like window strikes, behavioral disruptions from artificial light, and noise pollution pose worrying threats for birds that share human-altered habitats. Continued research into the way birds perceive their environment may be the key to protecting their future.