Sounds like she doesn't trust you nor does she like to be "caged" inside your home.

Actually, I put the box in the barn since I figured that's where she felt comfortable enough to have her kittens. She's not our cat (we don't know where she came from), and so I knew she wouldn't want to be in our house. Plus, I didn't want to move her from the place she selected.

Hmm might be the "human" scent. Just like many wild animals she might have been afraid of the smell or unfamiliar with it.
Before you know it though you might have a pack (don't know what the cat version of packs is) of cats in there

That may be. I know she's used to humans since she does have a flea collar on, but she's definitely not familiar with our scent since we're not her owners. I'm happy she chose our barn though, they've made for some excitement and some more opportunities for using Gimp.

True that.

Can't to wait for an update. The have such thick spiky fur.

On a side note, several of you commented on the kitten's claws. I found out here ( http://www.petplace.com/cats/developmen ... page1.aspx ) that kittens are all born with their claws extended; they are unable to retract them for the first few weeks. Apparently it helps them move about, and keep them in place when feeding.

oh yes now i remember, little kittens are more stingy because even when they have no intention to use for defense (or for climb on cloths , armchairs and alike) their nails are always extended

I was able to get a picture of the Mama in her new "house". One of the kittens is laying next to her stomach.

Very cute.
Lyle my first guess was also Porcupine babies.