It depends on what type/size your birdhouse is if it would be suitable for other birds. Some of the wren houses are awfully small for a Tree Swallow or Bluebird to nest in. Bluebirds need a 1.5 inch hole, swallows prefer that too but can get in a smaller hole. Chickadees also prefer the 1.5 inch hole but can get in a 1 1/8 inch hole. A housewren will enter any size hole, not much deters them except keeping the nestboxes far away from brush and trees. House Sparrows can enter a 1 1/4 or larger hole, you would want to keep them from nesting in your birdhouse. A properly mounted nestbox is mounted on a slick metal pole with a predator baffle and at least 15-30 feet away from trees/fences/brush with no branches hanging over the box. Squirrels and or raccoons can and will get into nestboxes placed in/on trees or mounted on wooden posts. A metal plate on the front is to prevent woodpeckers from enlarging the hole. If the nestbox is mounted properly squirrels shouldn't be able to get to it to chew the opening. Here is a link to "lots" of info about cavity nesting birds..it is a bluebird site but has load of info about all cavity nesting birds and how to attract them and properly put up nestboxes for them.... Donna Here is a link that might be useful: Cavity nesting bird info.....sialis...

Silvamae is our BirdHouse Queen!!! Yes you can get sanded grout at Home depot and sealant also, I go(cuz I can in my town) to a specialty tile store and buy outdoor mortar and outdoor grout and sealer. I am finding that even with that, certain tiles/dishes I have used, still crack/chip off with the freezing!!! grrr! All that work and WHY don't I ever bring stuff in for the winter!?!? Ususally I enjoy having "something" out in the yard to still look at after the plants die down, then it gets so cold I just never wanna get out there and haul some of that heavy stuff in the shed

The birds you list for the hole size do not nest communally. Purple martins, in the east, do, but the holes are generally made larger for them. It might have been intended for roosting (at night), but the design does not seem to be appropriate for that either. I'm going to throw another possibility out for consideration. It might be a nest box intended for a caged exotic species. Some of them might use the smaller holes, and nest communally. But I don't know enough about the nesting habits of exotic finches, etc. to be able to tell you if that might be likely, or not.

KS, that cute box isn't really good for bluebird nesting. We need to be able to get inside of a bluebird house to clean it out, check in on babies when young (yes, when we provide housing, we are obligated to help a *little* ;) - etc. It IS an adorable house, though. I'm not familiar with roosting boxes like gyr posted about. ! For more (very important) info about bluebirds if you're interested, see a great bluebird site