They certainly appear to be mites of the genus Ornithonyssus, most of which are parasites of birds, although some species are associated with rats -

https://bugguide.net/node/view/96991/bgimage

Most likely, they are coming from bird nests that have been built close your windows. I recall that ...

Hello everyone,
So I live in Spain (in Madrid precisely) and we've all of a sudden found a plague in our appartment. We first thought that it might be bedbugs, because we found it in the sofa, but looking at it more closely, it doesn't look like the species that is supposed to be associated to ...