Cuckoos refers to:
Simonian Cuckoos, the descendents of Simone the Fowl, or other cuckoo chickens (of which Simone was one).
The Cuckoo Count, also known as Charles the Cuckold, who cuckolded the original Lord Steadfast and took his place (20.13).
A cuckoo features in the Rhyme of the Sanguine Lords.