If you have problems with voles or squirrels eating you bulbs you can use bulb cages to protect them. They are simple to make.
1) Cut a piece of wire to form the four sides of the box. Calculate the length of the wire by multiplying the width for the box size you want by four.
2) Bend the wire to for a box.
3) Bend the individual wires around the wire on the opposite end to secure the box.
4) Add a bottom and secure it the same way.
5) Dig a hole to bury the bulb cage.
5) Place in the location where you are planting your bulbs. You may leave some of the cage above ground or it may be just below ground lever or the mulch.
6) Fill the cage with soil and your bulb(s). Add a top.
You may want to use a wire that has larger holes for the top to allow larger stems of lilies or other bulbs.