And thank you for understanding, I am just sorry your kids won't be able to get those chicks from me
Ridgerunner, the main reason I think it is raccoons, is that my neighbor had been having problems with them coming on her back porch and eating her cat food. So, I know that they are around here, and I know that they are not afraid of taking food even from people's porches! Also, this animal (these animals) came over the fence to get the birds from their pens, there was absolutely no signs of anything digging anywhere.
mmtillman, I am sorry for the birds you lost, too!
Awww, I am so very sorry for your loss. I can't say for sure what got them, but know they can leave large numbers of feathers behind just struggling. There's a slim chance that some of them could find their way back home, I hope so if it's at all possible.
Get yourself one or more live traps, like the Hav-a-Hart traps sold at Home Depot. There are other threads here about what to use for bait, and what to do with the animals you trap. Have your plan in place before you trap a predator, and pleasepleaseplease do NOT plan to release it far away from your place. One man's wilderness may be the edge of another man's property.
Perhaps you could speak with your neighbors about leaving cat & dog food out & available, especially after dark. And also about keeping their garbage cans covered & secured. Animals like raccoons, opossums, & skunks have actually had their populations increase due to development in formerly wild areas. Their predators have been eliminated, but their food sources have expanded with all the pet food & garbage cans, and they're not shy about living near human habitation.
To understand how they got them. Your birds were in a pen and not locked up in a coop?
The fence... I am not sure what it is called, but it is about 1" x 2" rectangles and 4 or 5 feet tall. The "egg flock" were in their coop, but the door was left wide open (because we have never had this problem before!). The Silkies were in a pen like this http://www.freewebs.com/gracefulbantams/chooseyourbird.htm but their nest box did not lock, so I think that was the "weak link".
The animal (or animalS) must have crawled over the fence, because there was no sign of digging anywhere!