What Is A Bluebird Trail?

Western Bluebird photo by Walter Ammann

The gentle and beautiful bluebird was once very common in North America.  The bluebird is a beneficial bird, eating many insects that ruin our crops and gardens such as cutworms and grasshoppers.  Today, the number of bluebirds has diminished due to habitat loss, overuse of pesticides and predators.

Bluebirds prefer open pastures and nest naturally in dead tree cavities and abandoned woodpecker holes.  Bluebirds can’t excavate their own nest cavities and depend on either natural or man-made cavities for survival.  Their natural habitat is being destroyed by man, and other bird species such as wrens, sparrows and starlings compete aggressively for their nest sites.  Bluebirds will readily use man-made nest boxes, and this may be our only hope of bringing the bluebird back to its original numbers.

Concerned citizens have created what are known as bluebird trails to help bring the bluebird back.  You can help protect the bluebird and increase their numbers by creating your own bluebird trail.

WHAT IS A BLUEBIRD TRAIL?

A bluebird trail is a series of bluebird nest boxes spaced about 300 feet apart.  Bluebird trails can consist of just a few boxes in a large backyard to hundreds or even thousands of boxes put up over large areas or stretches of countryside.  It is not necessary to have an entire bluebird trail to help.  A single nest box appropriately placed can attract bluebirds to your backyard.

CORRECT DIMENSIONS FOR BLUEBIRD BOXES 

A good bluebird box should have a floor size of 5″ x 5″, the box height should be between 8 to 12″, the entrance hole should be about 6 to 10″ above the floor and the diameter of the entrance hole should be 1 1/2″.  Be sure your boxes are made of durable wood like cedar or redwood, have ventilation holes in the top and drainage holes in the bottom.

Another good feature is an easy open front or side to check on the progress of the nesting birds without disturbing them.  Check the link to birdhouses in the right column where you can find my book on building birdhouses: Build Your Own Bluebird House

HOW TO MOUNT YOUR BLUEBIRD BOXES

Bluebird boxes can be mounted on poles, fence posts, utility poles or trees.  Posts or poles are the best for providing protection from predators.  You can purchase commercially available posts from your local hardware store or use existing fence posts or utility poles.  If you use a fence post, be sure to mount the box where livestock can’t get to it.

When possible, face the boxes toward the next fence post so that the birds can look into the entrance hole from a perch.  Mounting on trees is less desirable because of the threat of climbing predators like cats, raccoons, snakes and squirrels.

The bottom of the nest box should be at least 3 feet above ground.  Ideally, it should be mounted 4 to 5 feet above ground.  There is no single compass direction that the bluebirds prefer to have the box facing.  Your main objective should be to deter climbing predators, but allow for easy monitoring.

Face the boxes away from prevailing winds.  In hot climates, face them to the north or east to avoid direct midday sun.  The most important aspect of mounting is to face the box toward some tree or shrub within 100 feet.  When the young leave the nest they will make an initial flight to safety.

WHERE IS THE BEST PLACE TO MOUNT BLUEBIRD BOXES?

Whatever you do, make sure you place your nest boxes in good bluebird habitat.  Not even the best bluebird house will attract bluebirds if it is in the wrong place.  Here are some guidelines to follow for good bluebird habitat: 

• Bluebirds nest primarily in suburban and rural areas. 

• During breeding, bluebirds hunt insects by scanning the ground from a perch, spotting an insect, then swooping down to the ground to get it.  Scattered young trees or shrubs, fence posts and lower branches of a lone mature tree make good hunting perches. 

• Sparse or low vegetation is also important since it enables the bluebirds to see and capture insects.  Cut meadows, mowed lawns and grazed fields are good. 

• Nest boxes should be at least 100 feet from brushy or wooded areas where wrens are likely to be and preferably at least 1/4 mile from farmyards or barns where sparrows live. 

• Good areas for bluebird nest boxes include open fields, fence rows, orchards where no pesticides are used, cemeteries, large lawns, golf courses, public parks, along open highways that are kept mowed and pastures. 

• Mountain bluebirds will nest in open conifer woodlands and in the cliffs or clay banks of river beds. 

• Proper spacing of your nest boxes is important.  Bluebirds are territorial when breeding and will claim territories of 2-3 acres.  Research shows they will generally not nest closer than 100 yards from the next box. 

• To keep swallows out, pair boxes 5–15 feet apart.  The swallows will only nest in one, leaving the other open for the bluebirds.

Mountain Bluebird photo by Walter Ammann

MONITORING YOUR BLUEBIRD TRAIL

The most important part of any bluebird trail is to monitor the nest boxes.  You should check each box at least once a week to be successful. Monitoring is important to keep house sparrows from using the bluebird box, checking on the health and safety of the bluebirds and recording their progress.  When observing your bluebird boxes, go quickly and quietly to the nest box, open it and look inside.  Contrary to popular belief, your presence will not make the adults abandon the nest.

Remove any house sparrow nests.  House sparrows are aggressive competitors for bluebird boxes and may even kill bluebirds to take the house.  A bluebird nest is usually a neat grass cup.  House sparrow nests are always sloppier than bluebird or swallow nests and contain grass strands and fibers haphazardly spread inside the box.  When in doubt, the best way to determine if house sparrows have taken over is to simply observe their presence.

DO NOT remove nests of any other birds as they are protected by federal law, while house sparrows, starlings and pigeons are not.  DO NOT monitor nest boxes after the nestlings are 12 days or older.  They may prematurely bolt from the nest.  When in doubt, never open the box, you will be doing a great job just by observing their progress.

The young bluebirds should fledge the nest within 16-23 days after hatching.  Remove the nest after they have gone and throw away.  Old nests left on the ground could attract predators.  The mating bluebirds should begin building a new nest within one week.  Clean out the boxes in late summer after the breeding season has ended and keep them up for winter roosting birds!

WHEN SHOULD I PUT UP MY BLUEBIRD BOXES?

Anytime and as soon as possible!  Bluebirds start looking for breeding nest boxes in February in the South and by mid March in the North.  Bluebirds will use them well into August, producing 2-3 broods per year.  Consider leaving your bluebird boxes up all year.  When the mating season is over, birds will use the boxes as winter roosts.

Thanks again to Walter Ammann for his incredible photos!