Just about anything. He comes from a dark brown egg. I am thinking the egg could be:
There is an outside chance it was from the CX's or Cx' rainbow cross, I doubt the cx though cause they are lighter. I do not remember getting a darker brown from Bert's girls , but in that case Bert would have to be the Dad and the legs would not be black on the front and there would be no black in the bird...whewwww LOL.
The Dad could be:
The white tips on the feathers make it hard to figure at all.