Toasty Warm

Although most songbirds lay one egg per day, they don’t start sitting on them until the last or second-last egg has been laid. That way, they can time when they start to hatch. When the female tucks the eggs underneath her, the eggs become warmer and get the cue that they can hatch when they’re ready to. If any eggs aren’t going to hatch, it’s usually the first eggs laid.