Broody hens will sit of fresh air - no eggs are necessary to trigger broodiness.
Here's a link to see if your cockbird is doing his thing -
https://www.backyardchickens.com/t/16008/how-to-tell-a-fertile-vs-infertile-egg-pictures
http://horseshoe.two61.com/files/2013/04/fertile-eggs21.jpg...