Nestlings grow fast -- really fast. It makes sense that minimizing the time before nestlings are able to escape predators is linked to survival of the species. To fuel this rapid growth, it takes a LOT of food.
Imagine having to feed your family-of-five every 30 minutes during daylight hours. Further imagine that you and your spouse have to go out, hunt, capture and return home with these meals. Finally, imagine that each hunting trip only yields food for one. You can trust me on this one: nestlings do not share!
At the time of year the Chickadee lays eggs, there are about 13.5 daylight hours/day. So ... that's about 135 hunting trips per day. Chickadees are smart. They produce only one brood per year.
So here you go ... watch them grow ...
(If you are into counting, you will notice these pictures are from two different Chickadee nests. We can sympathize with the parents of the family of 6!)