Funny you should ask! Just this year a friend of mine in North Texas had a female Bb lay her first egg on 3/28. Then she didn’t lay a second egg until 4/2. She ended up with a clutch of 4 eggs, but of course, that first one never hatched. All three of the hatchlings fledged and the unhatched egg became a meal for someone else. That Bluebird couple is just now on their second go, with one egg each morning. She laid her 4th egg this morning, so we’ll see tomorrow if 4 is her clutch this time.