Amazing. I'd never have expected Merlins to go that far south and into such a hot and dry climate. Ours live mainly on small birds and mice which both would be rather rare near the salt lakes, I imagine.
Well it is pretty cold and wet (with snow) right now; when I saw the bird we had gone about two weeks without temperatures above freezing. We're well within the merlins' winter range, and there should be plenty for them to hunt. I've seen them in rural areas before, but never in the suburbs.