Your guy may just be looking for a mate, as suggested.
But if you are worried about him, there are many things you can do to try to find him: post ads on craigslist, put up flyers, call feed stores, animal control, humane society, animal rescues, local vets, etc. And then call again - you may...
They look very happy!
It is great that they are settling in, and that they can roam freely.
Your farm seems to be a lovely setting for them.
By the way (off topic, sorry), I love that last photo-your rooster looks giant (maybe he is?).
Makes me think of those old "exaggeration" postcards...