Bunnies, chicks, and eggs are symbols of new life so you can see how they would be associated with Easter.  Butterflies are also symbols of Easter. Their whole life cycle is meant to symbolize the life of Jesus Christ. The first stage is the caterpillar, which stands for Jesus' life on earth. The second phase begins from the cocoon stage, portraying the crucifixion and burial of Jesus. The third and final stage is the butterfly, representing his resurrection. We have books on Easter customs and traditions and stories about Easter bunnies.  There is even a book that will tell you what to do with that cute little chick someone gave your child (Free-range chicken gardens : how to create a beautiful, chicken-friendly yard /Bloom, Jessi.   636.5 BLO).  Here are a few more suggestions: 

Celebrate Easter with colored eggs, flowers, and prayer / Heiligman, Deborah. J 263.93 HEI 

The bunny who found Easter  Zolotow, Charlotte / E ZOL

My First Easter / DePaola, Tomie, E DEP

A tale for Easter/Tudor, Tasha  J 394.2 TUD

Oh, happy, happy day! : a child's Easter in story, song, and prayer /McKissack, Pat, J 232.97 MCK