Any guess on what breed this 3 year old hen is?

[Sonoran Silkies]

buff brahma cross; possibly with orpington. I don't really see anything that makes me think RIR or any sort of production red.

 

[Ducks and Banny hens]

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I would agree with you about the brahma part, but because of genetics, the color is not limited to having a Red parent. I think Buff Brahma X Light Brown Leghorn.