About us: We own the Wild Birds Unlimited nature shop in East Lansing, Michigan,
a store that provides a wide variety of supplies to help you enjoy the birdwatching hobby.

This blog was created to answer frequently asked questions & to share nature stories and photographs.
To contribute, email me at bloubird@gmail.com.

Thursday, June 30, 2016

Drain holes required in decorative bird houses

I have wrens nesting in a decorative birdhouse that I never intended them to use! I am thrilled that this happened, and luckily there is a hole (covered with a movable piece of tin) in the back, so I can clean out the house when the wrens are done with it. However, I don't believe there are drainage holes in the bottom of the house. Should I make some? Or doesn't it matter?

Overall it is a good idea to at least have at least one drainage hole in a bird house. This lets rain water out the bottom and allows for a little air circulation to keep mold and bacteria from multiplying. Decorative houses at grocery stores are sometimes really cute but there are certain things you should consider when purchasing a house to keep your birds safe and secure:

1. Proper Drainage
Proper drainage holes and a nice roof overhang makes for a nice dry house even during the rainy season.

2. Insulation and Ventilation
In the hot sun or cold winter months, untreated 3/4" thick wood, recycled plastic or ceramic houses give the house proper insulation. Make sure if you purchase a house with a metal roof it is only placed in the shade. Proper ventilation, a slit or opening at the top, is also important so hot air can escape.

3. Entrance Hole and House Dimensions
Studies show the inside dimension, the shape and the diameter of the opening determine what birds it will attract. To keep predators from the raiding the nest, an entrance hole of a basic backyard bird house should be no bigger than 1½ inches. The 1½ inch opening allows bluebirds, swallows, wrens or sparrows access, the 1¼ inches allows access to only the smaller birds like titmice or chickadees. And the 1 1/8 inch is only used by the tiny House Wrens. If you have a decorative house with a larger hole, a metal portal protector ring can be added to correct the size. You should also remove any perch at the entrance to deter predators.

4. Monitoring and Cleaning
Look for a house with easy access to the inside to monitor bird nest or for easy clean out. It is best if you can clean out your house at least once a year in September. By cleaning out a nest box you help deter parasite infestation, a predator’s ability disturb a nest through the entrance hole and it’s a good time to evaluate the house’s condition.

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