I have three chickens in a small coop. One is a silkie the other two are bantam mixes (regular feathered). When is it too cold for a silkie? It is 39f this morning (much lower last night) and she is huddling in the coop by herself. Should I worry? I do have diapers and could bring her in, but I don't want to if I don't have to. Thanks in advance!