When I took Boo-boo (the stray which Karen and I adopted) to the vet, to have her checked out and given her shots, I asked if she had been spayed. (If she hadn't, I would have had her spayed then).
The vet said that she couldn't find a scar, but that the cat had probably been spayed, because it would be highly unusual for a cat to be declawed but not fixed.
Well, naturally, Boo-Boo is now in heat. All the signs are there: the constant caterwauling in the middle of the night. The odd walk. The rolling, rubbing and stretching. The escape attempts. Only three to five more nights of cat screaming before we'll finally have a respite. And then it'll be time to go back to the vet.