We set up the chicks on Wednesday and went to the land for less than 2 hours... when we came back they were peeping and piled in one corner. I presumed they were cold or hungry so tweaked things a little and went to pull garlic. I checked them a little later and they were still piled in the corner so I decided I'd better pull them out and see if there was any reason for their stress behaviour (the temp was 90 which should be just fine).
At the bottom of the pile there was one little chick with blood on his back. WEIRD. I felt carefully around the brooder - no edges, nothing apparent that could do such damage. I thought about it while looking at the chicks and suddenly realized the chicks were taking up less room than they had earlier.
I counted them. Including our injured boy there were 13 chicks. Where on earth had 8 chicks gone in 2 hours? And how?
Still not positive but strongly suspect either a rat or snake got into them somehow. We were shocked and sad but glad that for most of the chicks the death was probably fast. (The injured chick also died)
The surviving chicks were a little traumatized for the day but, have been moved to the enclosed front porch, they are recovering nicely now. It's amazing how fast they grow.