2014 Tree Swallows

Three weeks ago while out in the garage I heard loud chirping to find two tree swallows circling low above the ground where I usually had my nest box. I had forgotten to put it out. Quickly mounting the box where I usually have it, the swallows entered it within a minute. They were clearly looking for last years nesting place. Three weeks later, I have 5 eggs. In 2013 I had 6 tree swallows fledge from their nest in the same location.