Birch are deciduous trees related to the oak and beech. They are found in many cooler places in the northern hemisphere. Birch are small trees that are grown in gardens for their attractive white bark.
A perch is something thin enough for a bird to sit on, holding onto with its feet. It can also be used for any narrow place a person or animal can sit.
You can also use perch as a verb, as in "to perch on something" or "the cat is perched on top of my head".
