This staining was found on the siding on a gable end with no soffit. There are no openings for bats which was the 1st thought.
Your first guess might still be right. They could be roosting on the c-channel.
Was it actually stained or was it some sort of fras from carpenter ants or bees?
Ny guess is bees.
I would agree – carpenter bee stains. Appears to be quite the infestation.
It looks to be falling from above - more on the upper sloped surfaces.
What is on the underside of the soffit area roof sheathing, painted dark, mold, ??
Bird crap? Seen similar when they nest in the eaves.
I thought carpenter bees leave a 1/4" hole. With that kind of infestation, the holes should be visible.
Bats can enter through amazingly small openings. Really looks like bat guano.
I had mice infested attics a few times and I seen these type of stains on the siding.
Here’s one with ice dam issues. The melting ice caused the mice droppings to stain the siding…
Bats don’t hang around in those type of tight eave areas. They hang from the most center portion of the attic.
I’m willing to bet that those are mice dropping stains. Whatever it is, it’s a total infestation.
Yes, carpenter bees make holes. The reason I say bees is when I was growing up we had a white garage that would get identical stains to those pictured each year. It was from bees (not carpenter bees) but I’m not sure what kind. We had regular bumble bees, wasps, honey bees, etc.