You pay for your order as soon as it is placed; that is what holds your reservation. We don't keep your payment information on file---this helps protect you from identity theft. But for that reason, we have no way of charging your card weeks or months later when your birds have hatched---or your juveniles are grown---and are ready to ship.
In addition, when ordering baby chicks in particular, if we did keep your payment information and wait to charge you on hatch day, if there were some problem with the transaction, it would create a BIG problem for the baby chicks! Living baby chicks are not like books or electronics, and can't simply be placed back on the shelf if the transaction doesn't go through. They must be shipped the same day they hatch in order to arrive at their destination safely.