I have been finding these little critters in my egg buckets. I have a stash of them in a cabinet I built into my chicken coop, accessible from the outside, right next to the nest box hatches where I collect the eggs. Some start in the buckets, but sometimes even a clean bucket will end up with more of these guys in them after I collect the eggs. I don't notice them on the eggs, but that doesn't mean I might have missed them.
Looking around on the internet, the closest match I can find for them are Spider Beetles. There are several varieties and each look a bit different, but I think it's a pretty close match. They are scavengers and will eat just about anything. Often they are found in food mills, or other storage locations, but they are happy to live off of feathers and bird or rat droppings as well. Sounds like my chicken coop would be a mecca for them. Lots of grains, feathers, chicken droppings.
The standard advice is to get rid of the food source. They will continue to grow in population as long as food is plentiful. The problem as I see it, is that I can't get rid of the food source. My chickens need to eat, and they will continue to create "droppings" as well. Plus broken eggs, feathers and other leavings from the chickens.
The good news is that they only eat dead stuff. No mention of them biting people or birds. No mention of carrying diseases. So they are relatively harmless, outside of them pro-creating and the risk of them infesting my house or cupboard. I need to be super careful about not bringing them into the house, which I fear I may have already done before discovering what they are.
I'm surprised that this isn't a more common thing. A search of the internet and of this web site turned up zero mention of this pest in connection with chickens or coops. Although there are plenty of references to "bird nests" as a source of food for them.
Anyone ever run into these before???
I started using DE in the coop after discovering them, but I have not treated the cupboards yet. That will happen after I give them a good cleaning to make sure there isn't any food in them, like cracked corn.