Bird mites are notoriously hard to catch. They are the size of the point of a pin, translucent, and quick moving. The glue traps used for mites don’t have pheromones, like moth traps do, so they don’t attract mites. Mites respond strongly to pheromones, so it would be a big improvement if mite traps were baited with pheromones.

There are diagnostic tests based on DNA for some species of mites. In the case of an infestation with one of those types of mites, identifying the cause of the problem just requires collecting DNA left behind by a mite—not a specimen of the mite itself.
See Research Associates Laboratory in Texas for more information.