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Fascinating Facts: Bird Senses, Songs and Sounds
Whether you live in the city or in the bush, most people wake up to the sounds of birds chirping outside. Depending on the bird the sound may be heaven on earth or a very rude awakening. The day when we do not hear the sounds of birds, we will know the end of the world is near…
A bird’s eye view…
Relative to their body, birds have a very small brain and eyes. Their eyes have a number of unique features that make for highly developed eyesight. Some raptor species have eyes as big as an adult human – this is enormous compared to their body size. So what make their eyes so special?
A bird’s eye is packed with significantly more visual cells. The retina contains two different kinds of visual cells – rods that are sensitive to light and cones that are sensitive to colour. Some raptors can have as many as a million visual cells. Humans only have 200 000 in their eyes, giving raptors their superior vision and allowing them to see in much greater detail. Bird’s eyes contain a special structure called the pectin found on the inner side of the eyeball that improves the bird’s sight as it has a special network of blood vessels that provide an important source of extra nutrients to the retina.
The retina of a bird’s eye also contains specially-coloured oil droplets, which may be shades of red, orange, green or yellow. These oil droplets acts as little light filters that filter out certain colours making a birds eye more sensitive to colours.
A bird’s eye processes information very rapidly allowing it to catch its prey and avoid an unexpected branch or structure.
Masters of hearing…
It is believed that the hearing of an owl is 300 times better than that of the average pigeon. Many people believe it is their ability to hear soft sounds, but it is actually the ability to pinpoint the location of their prey very accurately. Owls are very sensitive to high frequency sounds.
In general, sound is vital for communication between birds – warning call of danger, the romantic song of a male to attract the female or the persistent call of a chick wanting food. Humans and birds hear sounds over a similar range, but the hearing of birds is more accurate allowing them to hear 10 separate notes compared to a human only hearing one note. This helps birds to identify each by its call.
Birds do not have an external ear, rather an ear opening, and a small hole behind the eye. Just imagine a bird with ears flapping as they soar across the sky…
Touch and taste…
The degree of sensitivity in the bill and tongue of a bird depends on how they feed. According to researchers, some birds rely heavily on their beaks for foraging. The bill tip and tongue are densely packed with sensitive receptors called “Herbst corpuscles” – sensitive to taste and touch.
Bending bills…
Some birds can bend a part of their bill. This ability is called “rhynchokinesis” taken from the Greek word meaning “moving snout”. A perfect example is the snipe with the upper and lower part of its bill able to bend along the lengths. Once it pinpoints its prey, the end of the upper mandible bends slightly upwards, allowing the tip of the bill to open. This allows the snipe to shift its prey along the length of the bill and into its mouth.
Communicating through smell…
Scent is a vital form of communication in mammals and is used to mark territories, to recognise mates and family members, part of courtship rituals and for self-defence.
Shearwaters and petrels are mainly active at night and by using their acute sense of smell are able to find their own nests sites in the dark.
Another excellent example of birds using their sense of smell are honeyguides. They are thought to be attracted by the smell of the honeycomb wax.
What is the difference between a bird’s call and a bird’s song?
A birds’ call can be described as simple sounds made by both male and female throughout the year that include warning calls for danger and begging calls by hungry chicks. Songs, on the other hand, are longer and more melodious mainly performed by the male in territorial display and defence or in attracting mates.
Romantic Duets…
Males of most species will woo the females with a solo performance, but a number of bird species of both sexes will sing together in a perfectly synchronized duet. So perfect, that it is sometimes very difficult to distinguish that the sounds are from two birds.
As many of these duetting birds live in thick vegetation and cannot see each other, the duet is thought to be a musical, rather than a visual effort to help enforce and maintain their bond.
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