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Attracting Bluebirds and Other Cavity
Nesting Songbirds in North Dakota

Establishing Bluebird Trails

Preferred Habitat

Selection of proper habitat to place several boxes or establish a bluebird "trail" is vitally important. Most people make the initial mistake of placing boxes in inappropriate locations. These decisions either create disappointment or may actually benefit recruitment of unwanted and undesirable birds such as the house sparrow.

Bluebirds are insect eaters and less competitive for nesting space than are other cavity nesters. Therefore, placement of nest boxes should be in locations away from heavily wooded habitat preferred by tree swallows and house wrens and near open fields where insect hunting, maneuverability, and visibility to avoid predators is adequate.

Generally, open rural country with scattered clumps of trees or low shrubs is best. Placing boxes too close to shelterbelts and wooded areas will attract house wrens and tree swallows, which are also beneficial bird species. Examples of good habitat include pastures, fields, edges of country roads, cemeteries and golf courses. The closer you get to buildings or urban areas, the more chance you will have problems with house sparrows which will actually kill bluebirds and their young. It is also a good idea to avoid areas where insecticide use is high.

GIF - open land habitat GIF - building habitat
Good habitat for bluebirds generally consists of open and sparsely vegetated land in rural areas where insects can easily be captured and competition from other cavity nesting species is minimal. Habitats that contain buildings or dense stands of trees attract house sparrows, wrens and tree swallows which often out compete bluebirds for nesting space.

Type of Nest Box

The type of box to purchase or construct to attract bluebirds is a subject of much discussion and there are probably as many ideas as there are folks who maintain bluebird trails. Ideas come from personal experiences and you will certainly have your own opinion after a few years of monitoring a few houses. There are, however, a few basic ideas that have proven successful for producing bluebirds and these guidelines provide a good place to start.

Wood is probably the safest and best material for nest boxes. Wood mimics the natural cavity, is readily available, easy to work with and provides good insulation qualities. The best woods to use are cedar or redwood which withstand the elements without being treated.

Choosing between different designs of wooden boxes available shouldn't preoccupy a majority of your time since most offer the same result for the birds. Simply insure floor dimensions are at least four by four inches for eastern bluebirds and five by five inches for mountain bluebirds. Avoid thin wood which will not maintain tolerable temperatures inside the box. Also, do not use varnishes or stain inside the nesting box. These may be poisonous to the birds.

Both ventilation and drainage holes should accompany any box. One-half inch vent holes in the side of the nesting cavity will insure proper temperatures are maintained inside the nest box. The same sized holes can be drilled into the corners of the floor to allow moisture to escape. Entrance holes for eastern bluebirds should be one and one-half inches in diameter and about one-quarter inch larger for the mountain species. Holes in an oval shape have also been developed now under the presumption that birds can access with less difficulty.

The box should not contain a perch and the roof should overhang the entrance hole to keep rain and sun away. The entrance hole should be about six inches from the floor of the nest box.

Finally, one of the most important aspects is that you allow easy access for monitoring. By hinging either the top, front, or one of the sides, birds can be checked at any time and nest boxes cleaned easily.

Plans for building your own bluebird boxes can be found in Plans for Building Nest Boxes. Boxes can also be purchased at a variety of retail outlets.

GIF - nest boxes
Nest boxes can be of a variety of shapes and sizes as long as they provide the minimum size requirements discussed above. Cedar or redwood weathers well and provides good insulation from the sun. Plans for constructing your own boxes are found in Plans for Building Nest Boxes.

Placement of Nest Boxes

Before you begin putting out any nest boxes, take into consideration the location of preferred habitat which was discussed above. Some locations may not be suitable for bluebirds at all but will be excellent for other beneficial species such as the tree swallow.

Remember, a bluebird trail does not have to contain a hundred boxes, it can be comprised of as few as two boxes. The first step is to draw a sketch of your property as you walk it, visualizing potential locations.

Boxes should be located in pairs about 100 yards apart. Ten to twenty feet should be left between boxes in a pair. Pairing the boxes will allow a more aggressive species such as the tree swallow or house wren to nest in one of the boxes first while allowing the second box of the pair for a bluebird. This strategy is all based on bird behavior because many bird species will not allow another member of the same species to nest in close proximity to their own nest but will allow another species like the bluebird to nest.

GIF - box spacing
Nest boxes provide better opportunity for bluebird utilization if they are placed in pairs at 100 yards apart. Distance between boxes in a pair should be about 10-20 feet. Pairing, as seen in above photo, will allow a more aggressive bird species such as the tree swallow to nest one of the boxes first, but will leave open the other box in the pair for bluebirds. Bird species rarely allow another like species to nest in close proximity to their own nest, but will let a different species such as the bluebird nest.

Nest boxes should be attached to steel posts if possible. Seven foot smooth steel fence posts work extremely well and allow easy attachment. Wooden posts allow predators to climb and access nest boxes more easily. If you do use wooden posts, predator guards can be attached. Instructions for these are shown in Controlling Competitors and Predators.

Don't attach nest boxes to dead or dying trees within a forested area unless you are attempting to attract house wrens, chickadees, or nuthatches.

The recommended height for bluebird houses is four to six feet from the ground. Bluebirds may nest in higher locations but monitoring, viewing and maintenance will be much more difficult.

Face the front of the nest boxes away from the prevailing wind and in an easterly direction to avoid the hot afternoon sun from shining into the access hole. More important than this, face the box in a direction in which the young fledgling birds can reach a perch within about 100 feet. If you are attaching boxes to existing fence posts within a cattle pasture, put the boxes on the side of the fence opposite that of the cattle so they cannot be broken off by the cattle.

If you don't have adequate habitat on your own property, consider approaching a landowner with your idea. Also, be sure to obtain permission before you attach any nest boxes to utility poles or other private structures.

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