The Eastern Bluebird (Sialia sialis) is a cavity-nesting bird native to the eastern US. Cavity-nesting birds are those which create nests and raise their young in tree holes (cavities). Due to habitat loss and increasing competition from invasive cavity nesters, bluebird populations were in decline during the early 20th century. However, conservationists discovered that bluebirds will readily nest in artificial cavities (bluebird boxes). Today, bluebird populations are on the rise, and the species is considered at least concern for extinction.
Monitoring bluebird boxes is a key task which ensures the success of bluebirds. By checking their boxes weekly, monitors can keep an accurate count of fledgling success, watch for signs of predation and mites, and ensure that invasive birds are not using the nest boxes. Data collected by bluebird monitors is submitted to the North American Bluebird Society.
I have been monitoring bluebird boxes since I first started volunteering with the Merrimac Farm Chapter. Our chapter manages several "bluebird trails" throughout Prince William County. On each trail, there are 5 or more bluebird nest boxes, which are checked weekly. Monitors keep a close count of the number of eggs laid, the number of young hatched, and the number of birds fledged. Watching this progression is both fun and rewarding!
Besides bluebirds, other native cavity nesters also use bluebird boxes. Tree swallows are common, but we occasionally see chickadees, titmice, and house wrens. Sometimes, we even get cowbird eggs! The boxes are designed to keep out predators (like snakes and raccoons), so they are very safe places for native birds to raise their young.
Bluebird monitoring season runs from March through August each year. Though it's too late to join this year, please contact us if you are interested in becoming a bluebird monitor for the 2025 season!
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