They are found where ever birds nest and most infestations occur during early spring and summer when bird nesting is most prominent.
Adult bird mites are barely 1mm in length and have no color until they take a blood meal and turn reddish brown. The eggs and nymphs cannot be seen without magnification. They have a very short life cycle and can grow in number rapidly. If no bird host is available they usually perish in several days.
All mites seek alternatives hosts. It is during these times that they may come in contact with humans. The bites can cause a rash and some people can feel them crawling on their skin.
Treatment: Removal of the birds and nesting material is imperative. The area should be cleaned and treated. Installation of bird spikes or netting will prevent future infestations. The interior of the home may not require treatment unless depending on the extent of the the infestation. Wet paper towels and vacuuming will remove most of troublesome Mites. The remaining Mites will die off in several days
Source: http://ento.psu.edu/extension/factsheets/bird-mites
