Hugh, on my first nesting of this season time got away from me, and I had 5 eggs before I realized that they were laying any. I immediately put up a wren guard (I had lost 5 eggs to wrens 2 seasons before) and the birds took to it within 20 minutes. HOWEVER, they had not started to incubate yet.
In your case I don’t know what they would do. I believe I would put one up, watch it continuously for their entry, and if they don’t go in within 30 or 40 minutes, take it back down. But I am NOT an authority as I’ve only been doing this for 3 years.BZ
Well I made a hinged guard and the female gave me an earful while installing it. When I checked back 45 minutes later she hadn’t returned yet or was out feeding. Since I hinged the unit I flipped it up and am waiting to see if she returns now with it out of the way. Hopefully I haven’t screwed up the works. On a more positive note, my other box is up to three eggs since the first one appeared 3 days ago.
Hugh
Hugh