A rooster's fertility usually diminishes as daylight dwindles in the fall, just like a hen's laying will slow down or stop. Hens can lay fertile eggs for about 3 weeks after a single breeding. 5 weeks ago, she could have been laying fertile eggs. The rooster's fertility probably started to drop sometime in November, but the girls could have continued to lay fertile eggs for several more weeks. It's also possible that the rooster prefers the Easter Eggers to the Ameraucana girls.
With the days getting longer now, he should start to feel a bit more randy and will begin to pursue relations with renewed vigor.