Girls do tend to go later but it depends on the bird - weight and size, health, presence of siblings, experience of parents, etc... Two years ago, the female at my site fledged on Day 38 with her brothers, last year they all (2 males and 1 female) were still on the ledge being beak fed at Day 42. In Edmonton, Cassie I think didn't go until almost/or on Day 50 - she was a lone chick. Last year the Hamilton females were all over 1000 g's and we thought for sure they'd take forever to fledge and probably come down - well they showed us! They flew like champs!
I can't speak for all falcons - nor would I attempt too but in my personal observations at my site I've noticed that now that we have the same adult pair for a few years - the fledge periods are taking longer as they've gained experience. I'm guessing the parents adjust their strategy based on past years - for example we have glass buildings so the kids would typically hit the glass on fledging and get hurt and in some cases die but now that they don't push the young as hard to go early and let them stay longer, we have had no fatalities for three years now during fledge and this year none of the kids have hit the glass on their first flights. The first year I watched my pair - the female was very aggressive in trying to get the young to fly early, she still tries but doesn't push them as hard as previous years and seems to be willing to wait until they are ready to go.
The longer they stay, for sure the better to get stronger.
