These are black sex link chicks. The roos have white feathers/down on their head, the females are solid black. So you know immediately what you've got.
Update: #2 is a roo, too! Of course...just my luck. LOL #3 hatched during the night, and I watched #4 hatch about 30 minutes ago. The last 2 are still too wet to tell about their sex yet. I'm hoping girl!
Mine went into lockdown at 7:30 this morning! My humidity is running nice and high.. so much so that I had to open one of the vents because of LOTS of condensation on the windows. Fingers crossed!