It looks like it came from some form of pest, but there are no obvious holes or material above it. It's between glass and a screen with no obvious openings or holes. None of my other windows have it. We did have the house re-insulated recently, but I don't think it looked like this. Any help identifying what's going on?
I'm geographically located in Northern NJ I'm the US in the suburbs.
It doesn't look much like termite droppings to me:
https://www.orkin.com/pests/termites/termite-droppings
What Do Termite Pellets Look Like?
Drywood termite pellets are tiny, oval-shaped capsules with six concave sides and rounded ends. These pellets, which are about 1 millimeter in length, can form small mounds beneath kick out holes. The mounds may look like small piles of salt or pepper.
