San Diego County California birds
There are various reasons you might not see the mother bird return - for example, she might be aware of some sort of threat that would make it unsafe for her to return just then. You might also just not see her returning. If it is taking her awhile to find food, there may be long periods of time when she is gone, then she could come back quickly to feed and then take off again. It is more advantageous for a mother to spend time looking for food than just "hanging out" with the babies. Of course, it is also possible that something has happened to the mother. If she hasn't come back for a couple days, she may have been injured or killed. If that's the case, you have two options: 1) do nothing. This seems harsh but in nature, not all animals will survive. It's usually best to just let nature happen. 2) call a licensed rehabilitator. Most birds in the U.S. are protected by federal law, so it is illegal and unwise to take the babies into your home and try to feed them yourself. A rehabilitator will have the tools and resources to take care of the baby birds properly.