Strange poop in the nest boxes

[aart]

Looks like cat poop to me.

Thanks for the images, those are very helpful. I already cleaned it out so I can't put anything next to it. It was a little bit smaller than a dollar bill.

What's the spacing on the peg board?
Most common is 1".

 

[imnukensc]

Looks like cat poop to me.

Could be I suppose, but I've never known a cat to not at least try to cover its scat.