Birds have a significant number of reduced muscles to help them reduce their weight. The most-developed muscles in birds are the flight muscles that they need to fly. The bones are mostly fused, reducing the need for muscles to hold the bones together. The skulls of birds are very thin and the beaks are very light.
It is called ACCOMMODATION. Accommodation refers to the mechanism by which the eye adjusts his optical power in order to focus properly on an object as the distance of the object varies. To achieve this, the shape of the lens has to be adjusted appropriately.
