Wrens are small, short-winged, long-tailed songbirds with quirky behaviors. These small, often drab-colored birds often hold their long tails semi-upright and collect insects with their down-turned long bills. The Carolina wren and the house wren are among the most common inhabitants of birdhouses, but making sure the dimensions are correct will allow you to keep these small birds while not attracting larger, invasive species such as starlings. Their house requirements are the same except for the hole size and height.
Wren Nesting Sites
The Carolina and house wren prefer to nest in cavities near brush piles or thickets. Without birdhouses around, these little wrens will seek out nearly any cavity, some of which could surprise you. Your hanging baskets are an ideal spot for Carolina wrens, as are the pockets on your clothing on the clothesline, according to Alabama Cooperative Extension System. Place the birdhouses near brush piles or thickets.
These small birds require small houses; they only need enough size for their nest and babies. The bottom floor of the house for both the Carolina wren and the house wren should measure 4-by-4 inches. The height of the sides should measure 8 inches tall angled down to 6 inches. It doesn't matter whether the top angles toward the front or toward the back; this will depend on where you place the box. This allows for a sloping roof that will help shed rain water.
The size of the entrance hole is one of the most important factors when it comes to designing a birdhouse for a native species. If the entrance is too big, invasive species or larger native birds can quickly steal the home from the wrens. House wrens require a hole with diameter of 1 1/8 inches to 1 1/4 inches. The Carolina wren requires a slightly bigger hole -- a diameter of 1 1/2 inches. Drill the hole approximately 4 to 6 inches above the floor.
The height of the birdhouse is also important, as bird species are particular about the location of their nests. Both the house wren and the Carolina wren prefer their nesting sites somewhat low, except the Carolina wren should nest a bit higher than the house wren. Hang a house wren birdhouse 5 to 10 feet above the ground; hang a Carolina wren house 8 to 10 feet above the ground.
Other House Requirements
When building a home for your native wrens, drill 1/8-inch to 1/4-inch holes along the side and bottom to allow for draining and ventilation. Recess the floor approximately 1/4-inch to prevent rotting. Design the roof to open on a hinge for simplified cleaning, and make it approximately 2 inches longer to provide an overhang that limits wind-blown rain having the opportunity to fall through the entrance hole.
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