I've found kittens! What do I do?
The first thing you ought to do is determine their age. Kittens should not be separated from their mothers until they are at least 8 weeks of age, if at all possible. Staying with mom is important for their development and increases their chances of survival if they are still on mother's milk, which is why we focus on keeping mother and kittens together first and foremost.
Leave Them Alone
This may sound counter-intuitive, but if you see young kittens who you suspect may still be nursing, leave them alone. Wait and watch instead, and do not disturb the nest. If Mom is nearby, she may just be waiting until she feels safe enough to come back. Wait to see if mother returns at all before bringing them inside and trying to find placement for them.
If the babies are under 1-2 weeks of age, it is CRITICAL that you give them the chance to be reunited with their mother. Very young bottle babies can be incredibly difficult to hand rear or even find capable fosters for. Although well intentioned, preemptively separating them from mother could lead to their deaths.
Friendly Mother Returns
Great, so you've watched and waited -- and lo and behold, Mother has been watching you, too! And what's better -- She's friendly! If possible, relocate them into a quiet spot in your home, a foster home, or offer to foster them until a rescue can take babies and mom. Try posting in your local animal groups and calling different shelters in the area. They may be able to point you in the right direction.
If you decide to care for them, help wean them onto canned food at around 4-5 weeks of age and help set them up to succeed in their new homes by introducing the litter box, too. Fostering can be hard, but it is very rewarding! All kittens and mom should be spayed/neutered before going to their new home in order to prevent the cycle from continuing.
Feral Mother Returns
Even if the kittens have a feral mother, it is important to let them stay with her until they are ready to be weaned at 4-5 weeks old. Nothing beats mother's milk, so it is critical that they stay with her if at all possible. If your home seems safe to her, with food, water, and shelter, she will keep coming back with the kittens, even if she moves away initially.
Keep her comfortable, and once the kittens are old enough, bring them inside. Handle them often for socialization, wean them onto canned food, and network them into a rescue or spay/neuter them before adopting out. Mother should also be live trapped and spayed, so the cycle doesn't repeat. Again, speak with rescues in your area to see what resources may be available to you for Mom.
Uh-oh... Looks like you're "Mom" now.
If they are under 4-5 weeks of age, they will need to be bottle fed. They must have kitten formula. Being fed milk from your fridge is dangerous and could hurt a lot more than it could help. Before feeding, their temperatures need to be stabilized. If you are committing to bottle feeding these babies, www.kittenlady.org has wonderful resources available to you.
If the kittens you've found appear to be over 5 weeks of age, they are ready to be weaned onto soft/wet kitten food and are old enough to be introduced to the litter box. By the time they are 8 weeks old, they will be ready for the next phase of their life in their new forever home.
Before They Leave
No matter the scenario, mothers and kittens alike should be spayed/neutered before going into their new homes to stop the cycle. Please reach out to local organizations, shelters, rescues, clinics, and animal control facilities to see what resources may be available in your area.