The snowy owl migrates from the Arctic to spend the winter in Alberta. All species of owls lay plain white eggs. These are laid over a period of several days. Incubation, and thus embryo development begins with the laying of the first egg. Eggs hatch over a period of several days.
Older nestlings are larger and have a greater chance at survival than younger, smaller ones.
This contrasts with the nesting habits of upland game birds and ducks, where incubation does not start until the last egg is laid. All young hatch at about the same time, and all have an equal chance at getting enough food. Young owls are cared for by both parents. Nestling owls are very demanding, having enormous appetites. They can eat their own weight in food in a single night.