What is the general parenting process of birds?

I am able to observe a nest of what i believe are sparrows at a very close range (they're in my garage)..at first, when i went out in my garage, there was always the mother and father..now..I only see one parent..where is the other one? Do they alternate in extended hunting trips and return later?What is the general parenting process of birds?
Yes, the birds do Alternate. When the one goes out for food the other one lays on the eggs. Even the male will lay on the eggs. Best answer please