When building a birdhouse or nestbox, the hole size (entrance) is one of the most important decisions you will need to make. Do you know that the diameter of the hole determines which birds will fit into the house and which birds will leave it alone? If the entrance hole is too large you might find less desirable birds are using your birdhouse.
If you are not sure which types of birds you want to attract, go with a larger hole size. This is because birds in general will use a bird house with an entrance hole larger than required. However, the birds will be at more risk from predators such as European starlings which are known for killing nestlings. Learn about the best locations for birdhouse placement.
Below are some optimum hole sizes for common cavity nesting birds. That is, birds that build nests and lay eggs inside a cavity or sheltered chamber.
Optimum Birdhouse Hole Size for Cavity Nesting Birds.
| Bird Species | Entrance Hole Size | Entrance Height* | Mounting Height |
| Bluebird | 1.5” (3.8 cm) | 6” (15cm) | 4-6’ (1-2m) |
| Chickadee | 1.25” (3.2cm) | 6” (15cm) | 5-15’ (2-5m) |
| Flicker | 2.5” (6.35cm) | 4” (10cm) | 6-10’ (2-3m) |
| House Finch | 2” (5.1cm) | 4” (10cm) | 5-10’ (2-3m) |
| House Sparrow | 3” (7.6cm) | 6” (15cm) | 10-15’ (3-5m) |
| Kestrel | 3” (7.6cm) | 9” (23cm) | 10-20’ (3-6m) |
| Nuthatches | 1.25” (3.2cm) | 6” (15cm) | 10-15’ (3-5m) |
| Owl | 6” (15cm) | 4” (10cm) | 10-15’ (3-5m) |
| Purple Martin | 2.5” (6.35cm) | 1.5” (3.8cm) | 10-15’ (3-5m) |
| Tree Swallow | 1.5” (3.8cm) | 4” (10cm) | 5-10’ (2-3m) |
| Warbler | 1.25” (3.2cm) | 4” (10cm) | 5-10’ (2-3m) |
| Woodpecker | 1.25” (3.2cm) | 7” (18cm) | 10-20’ (3-6m) |
| Wren | 1.25” (3.2cm) | 4” (10cm) | 6-10’ (2-3m) |
*Entrance Height – location of hole above floor.
Where to mount the birdhouse.
To attract nesting birds, it is important to mount or hang the birdhouse in the ideal location. Below are some factors to consider when deciding on where to place a birdhouse.
Birdhouse Location.
Purple martins and bluebirds prefer birdhouses that are in open areas. Most other birds prefer concealed areas that help camouflage the birdhouse. The parents like branches nearby so they can keep an eye over their family.
Birdhouse height.
In general, the higher the bird house the more protection the house provides from cats and other predators. The chart above list the recommended heights for mounting birdhouses for various bird species.
Image Version of Birdhouse Hole Size
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Bill and Jodie Rosener | (918) 456-4482 | Tahlequah, OK 74464
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Thank you, just the information I was looking for.
What size opening and mounting height for a cardinal?
Jan, cardinals are typically not cavity-nesting birds. They prefer to make their nest in the branches of trees rather than in an enclosed space. So making a birdhouse for a cardinal will most likely be in vain. However, the wrens, bluebirds, and sparrows will gladly thank you. Bill
The swallows are pretty but they chase all the other birds away. Last year I had a pair of sparrows and robins nesting in our houses but after the swallows appeared and bothered them the other birds cleaned out the houses and left.
is it useful or detrimental to include a perch (dowel or flat surface) outside the hole? if so, how far from the bottom of the hole? Dan
Dan, I believe a perch has more advantages than disadvantages. A perch allows a bird to land when carrying nesting materials and then push the materials inside. A perch also allows a bird to examine its surroundings before entering the birdhouse. I typically place my perch approximately the same distance below the entrance hole as the size of the entrance hole. For example, if the entrance hole is 1.5″, I will place the perch 1.5″ below the entrance hole. Bill
I wanted to build and donate to our local walking trail 10 bird houses I want to do it the most cheapest way but safest for the birds what wood do I use and do I put a water protectant on it as well?? If that project goes well I would like to build more for other area’s. Can anyone help with my question?