A stray cat has given birth to some kittens in a store room in my house where no one goes. She goes in and out from a window that's broken. The window is high above the ground.
I noticed that when she was on her way to go inside, the kittens started meowing. The mom had not made any noise, neither could the kittens see her coming.
The kittens, at a guess, are about 2 - 3 weeks old.
How did they know that mom is coming?