Don't even think about taking in that seemingly abandoned baby bunny in the yard. Wild baby bunnies almost always die in captivity. That nest of bunnies you found probably isn't abandoned, anyway. Mother rabbits usually make their nests out in the open, and come to nurse their babies about five minutes during the middle of the night, then leave for the rest of the time. The mother probably is coming back, but if you move the bunnies, she will be extremely distressed trying to find them.

If you disturb the nest, try as best you can to cover it back up the way it was and then leave the baby bunnies alone. Leaving them alone gives the bunnies their best chance for survival. If you know for a fact the mother has been killed or if the baby bunny is injured, immediately contact the humane society to find a skilled wildlife rehabilitator. Rehabilitating a baby bunny is extremely tricky, and most people won't be successful trying to do it themselves. For more information about this subject, see the House Rabbit Society's Web page.