Raining leaves

Sitting at home today for the second day in a row of being sick, I watched the birch tree outside our kitchen window shed almost all of it's leaves in one day. At times they came down in such large quantities you would think someone was up top grabbing handfuls at a time and throwing them. It was if I was watching something out of a movie where the props person was dumping them from above the set.

I wonder what makes a tree decide that today is the day to give up their leaves? And why other trees seem to linger forever, often well past the first snows before grudgingly letting go? Are the oaks more stubborn than birches? Are our maples weaker still since their leaves have been gone for a week or more? I guess I want to be like the oaks, not giving in until the inevitable.