Leave It Be
Even though you might want to scoop it up, unless the kitten is in immediate danger, the best thing you can do for it is to leave it alone. The mother cat is probably out hunting, or she could be moving her litter to a new location. Either way, she most likely will return soon. Kittens who are taken away from their mothers too early are at a disadvantage both health wise and developmentally. The best caretaker for a young kitten is its mother.
Alleycat Allies advises that if you find a young kitten, or a whole litter, opt to save their lives by leaving them with their mother in their outdoor home. You can help by providing food, water and shelter from the elements for the mother cat.
For more information go to www.alleycat.org