Is the opening small enough to prevent birds, chipmunks or baby rabbits enter this trap?

Thank you for your question about the Tomcat Rat & Mouse Killer Refillable Rockscape Bait Station. Chipmunks or animals similar in size to squirrels might be able to get in to the bait station and access the bait. To reduce chance of non-target animals getting bait be sure to place station along the house or building walls. Do not place close to bird feeders which tend to attract squirrels and other small animals.