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Sylvilagus floridanus
ForestDragon has given good advice. The general rule is if they are the size of a tennis ball then they are ready to leave the nest. They do often hang out with their litter mates for the first few days but are perfectly able to fend for themselves!
As long as you put the baby back where s/he was found everything should be fine. Mom rabbit won't abandon them if you handled them. It looks almost old enough to leave the nest (they wean at four weeks). Mom will visit them but not often (maybe twice daily) to avoid drawing predators to the nest. Very cute!
Yeah, my niece spotted about 4 of them hunkered underneath the deck.. Not sure she should have picked 1 up, but it was already done. Now we have to make sure momma isn't spooked, and comes back to them.