According to ornithologists, the hearing abilities of birds are similar to those of man. Birds have ears for hearing which are in many respects similar to those of reptiles. The outer ear consists of a short external passage or meatus, ordinarily hidden under the feathers at the side of the head. Most birds have a muscle in the skin around the meatus that can partially or completely close the opening. The tympanic membrane bulges out. From the inner surface of the tympanic membrane, an ocular chain transmits vibrations of cochlea. The chain consists of an osseous inner element, the columella and a cartilaginous extra-columella that extends the columella peripherally and connects with the tympanic membrane.
It has been observed experimentally that most of the birds respond over a frequency range from 100 to 12,800 Hz. The frequency range of human ear is from 20 Hz to 20,000 Hz. Birds can separate sounds which appear as continuous to the human ear.
Birds use their hearing power to guard themselves against enemies and other kinds of danger. Some birds also use vocalizations to identify their mates or group member. Owls locate and catch their prey by auditory cues.
Birds are warm-blooded animals of the class ‘Aves’. Like mammals they are vertebrates. They do not bear their young but lay eggs from which they are hatched.
Birds have feathers, wings and beaks that make them different from other animals. They don’t have any teeth. They mainly feed on insects, seeds and animal flesh. Their sight is well-developed and highly efficient, but their sense of smell is rather poor.
There are about 9000 species of birds. They range in size from the tiny humming bird of about 5 cm in length, to the ostrich, which can grow 2.5 metres in height and can weigh as much as 136 kg!