QUESTION: Every year Carolina Wrens nest in my front and backyard, either in the hanging plants, generic birdhouses I’ve received as gifts, etc. This year I bought some wren houses from Woodlink but the opening is only 1″ round. In googling it, I see “expert” sites contradicting themselves – recommending 1 1/8 or 1 1/2 or larger, depending on whether attracting House Wren, Carolina Wren, etc.) Anyone know what size I should enlarge it to?Anonymous
ANSWER: Good question, which is my statement any time I do not know an unequivocal answer.
I do know that Carolina Wrens are opportunists nesting in cavities or any tight area like a planter as Mary has experienced, crotch of a tree, old pair of pants hanging in a garage (personal experience), or vine tangles. They can nest in a box with a 1 inch hole or a box up to a 1.5 inch hole, the recommended size for the Eastern Bluebird or larger. Most places recommend a 1 1/8 inch hole for Carolina Wren and 1 inch for House Wren. One of the primary reason for having a small hole is to prevent House Sparrows and European Starlings from using the nest. Neither of these species are an issue on Seabrook Island.
Choosing a larger hole opens up the potential for a variety of species to use your box.
Regardless of the size hole chosen, one may find that the House Wren will eventually usurp the box, most often filling it to the brim with sticks so the box cannot be used by other birds. Unlike the Carolina Wren, the House Wrens have a strong preference for nest boxes and more open, less shrubby areas.
One of the way to manage and encourage Carolina Wrens is to be ready early in the season. They should be laying eggs by mid-March. The House Wren will not be laying eggs until the first of May. This behavior allows the Carolina Wren to have its first brood prior to the House Wren even starting. The Eastern Bluebird starts in Mid-February.
Hope this helps.Bob Mercer, SIB’s “Resident Naturalist”