A birdhouse at Swan Lake Bird Sanctuary - Tree swallows. We put up birdhouses to help and attract birds, but sometimes our good intentions lead to disaster. Hole size is important. If it is too big, predatory species can get in and take the eggs or chicks. A perch also makes predation easier; birds don't need one, as they are fully capable of accessing the nest without it. In the spring, when nesting begins, the air is cool and the sun rarely causes heat issues. As the season progresses into summer, the risk of heat exhaustion to the vulnerable birds increases. Putting the house in the shade or having some kind of insulation reduces the likelihood of their death. Lots of ventilation also helps to encourage air circulation; just make sure the vents are not too large. Birdhouses don't need a perch, but their walls can't be smooth either. Rough, unsanded wood is all that is needed for the birds' access. You can build the house out of plywood ...