Question: birds and dolphins have no eyes ,how do they know there is an obstacle on their way

Daniel Mbuthia answered on 20 Jan 2017:

Birds do have eyes, so do dolphins. In fact birds have a very good eyesight. The eagle can spot a rabbit from about 3 kilometres away. Other birds like the owls are nocturnal and can see at night while birds like the gull can see under the water to locate fish. Dolphins have a good eyesight both in water and outside the water. Both dolphins and birds rely on their eyesight to escape predators and find food. The only exception is the indus dolphins which are found in the Indus river. They are considered blind and so they rely on echolocation to navigate the waters and find food. Other dolphins also use echolocation- They produce high frequency clicks, which creates sound waves that travels in a very high speed through the water. These sound waves bounces off objects inside the water and return to the dolphins as echoes. Dolphins are able to pick up these echoes through their lower jaw, direct the sound to their ears and then on to their brains where they are interpreted and so they can tell the shape, size or even movement of other objects near them.