This single window mounted unit contains three separate dwellings with the entrances to each slightly angled away from the other. Picture three birdhouses side by side with the one in the center facing forward, the one on the right facing a little to the right of forward, and the one on the left facing
a little to the left. There are two protruding dividers between them to keep the entrances semi-private, and the interior dividing walls are insulated for soundproofing. The unit mounts in a window much the same as an air conditioner does only it sits flush with the inside of the window (its lightweight). Most of the unit is suspended beyond the window. Insulated flaps extend from each side to close the gaps in the open window.
The front and bottom of each dwelling are removable panels that slide in airtight grooves. The face panels (entrances) come in an unlimited number of styles. Different birds prefer different entrances. Some birds prefer a small hole and a perch, others prefer just a larger hole, some are attracted to colors and patterns, etc. Depending on the birds in your area, and the ones you want to attract, select the appropriate face panels. This also makes for very easy cleaning in the case of migratory birds where you have to remove the nest yearly. And if a family moves out and you want to try something new, clear out the nest, clean the bottom panel, put on a new face panel, and youre good to go. All this can be done without major disruption the other occupants.
For those of you who enjoy bats (as I do - mostly because they eat thousands of mosquitoes), just put the bat hanger attachment in, use the solid face panel and the bottom panel with the slot cutout. Done.
The back of the unit (the side inside your house) is made of three half silvered mirrors. It comes with an attached hanging curtain to cover the mirrors. The curtain has suction cups at the bottom so when you want to lift it you just flip it up and stick it to the window. Each mirror is parallel to each entrance respectively, and there is a blackout spot on the center of each so the birds dont see themselves and freak out when they first peek through the hole. Each dwelling has a very dim (adjustable) light inside that stays on all the time. This will not deter them from building a nest (during daylight), and will not bother them at night since the change from light to dark is gradual and its no brighter than moonlight. The inhabitants can be viewed and enjoyed night and day so long as the room is darkened (otherwise leave the curtain down).
The birds get the added bonus of a little warmth from your house on those cold winter nights. Put a feeder out for them. They get a happy home you get a great view.