1. Eastern Bluebird (Sialia sialis):
- Northern populations: late March to mid-April
- Southern populations: late February to early March
2. Western Bluebird (Sialia mexicana):
- Northern populations: mid-March to early April
- Southern populations: late February to early March
3. Mountain Bluebird (Sialia currucoides):
- Northern populations: mid-April to early May
- Southern populations: late March to early April
It's important to note that these are just general ranges, and the exact timing of egg-laying can be influenced by various factors such as weather conditions, food availability, and nesting site competition. Bluebirds typically lay their eggs in cavities or nesting boxes, and they may have multiple broods per season.