Birds such as crows, pigeons, and sparrows have three toes in the front and one toe at the back. They use their toes to hold tree branches or wires tightly, so as to sit on them. This is called perching. These birds can also sleep while they perch.

When a bird has to fly, it flaps its wings both in upward and downward directions. The upward and backward movement of wings is called upstroke. The downward and forward flapping of the wings is called the downstroke. Downwards and forwards orientation of wing is more spread in area in comparison to upwards and backwards. When wing go backwards, it gets partially folded. Therefore when the bird has to create more lift it brings its wing more forwards.