From Ground: If the bird cherry is currently in the ground, start by
watering it to dampen the soil. This makes it easier to dig the plant out without damaging the roots. Next, dig around the plant with a spade. The goal is to get under the root ball, without breaking it or damaging the roots. After this, carefully lift the plant out of the ground.
From Pot: If the bird cherry is in a pot, water the plant first. Then turn the pot sideways, hold the plant gently by the stems, tap the edge of the pot against a flat surface. As the plant loosens, continue tapping until the plant slides out, cradling the root ball with your hand.
From Seedling Tray: If the bird cherry is in a seedling tray, water the soil first. Use a trowel to gently loosen the soil around the plant. Once loose, you can lift the plant by the base, and it should slip out easily.