A bird sitting on the floor of a wire cage and is in hand boy .The starts flying .Will experience any change weight cage?

Yes the weight of the cage will change .When the cage is at rest on the floor ,the cage exerts a upward force on the floor (normal force) equal to its weight .When the bird starts flying the cage looses contact with the floor and hence the normal force becomes Zero .In the absence of floor and hence the normal force becomes Zero .In the absence of any other external vertical forces , the weight of the cage decrease by the weight of the bird