Ontario Eastern Bluebird Society

Eastern Bluebird Conservation in Ontario

by Don Wills

Ontario now has a stable Eastern Bluebird population due to the tireless work of dedicated conservationists who have provided the birds with safe, predator proof nest box trails. Eastern Bluebirds were nonexistent in my farming community until I started setting up boxes. After 16 years of careful nest box conservation, this area near Caledonia now has the highest density of bluebirds in Ontario. Tree swallow, house wren, wood duck and many other cavity nesting species have also benefited from nest box programs.

The following information is a general guide for proper nest box setup in Southern Ontario. Eastern Bluebirds are highly adaptable to a variety of habitats found in rural Ontario. Their varied diet goes from completely insects during the nesting season to wild fruits such as Staghorn Sumac and Buckthorn throughout the fall and winter months. In my area of Southern Ontario, many Eastern Bluebirds overwinter depending on Staghorn Sumac and available roosting in empty boxes for warmth.



The best habitat for bluebirds is a grassy open area with mature trees for hunting perches. Areas that are mowed throughout the nesting season provide easy insect hunting and enable the adults to remain close to the nest box for protection from possible nest predators such as house wrens or mobbing tree swallows. Hayfields, large cemeteries, road right of ways, large well kept lawns and especially pasture fields make great habitat, usually creating conditions for more than one brood per season. Bluebirds can have as many as three broods if food and weather conditions are ideal. Nest boxes must be set up at least one half-mile from farm buildings to avoid house sparrows. These European imports are the number one enemy of the bluebird and tree swallows and will guard boxes killing any nest competitors. In box trapping is sometimes effective but house sparrows and bluebirds will never live peacefully together.

Nest Box Design

There are many proven designs available and I have experimented with practically all of them. The two designs that I have used for years with great success are the standard square (North American Bluebird Society) box with a modified front door opening system and the slant roof Peterson design which is highly water resistant and has an easy to monitor pull down door. Other designs used successfully by bluebirds in Ontario are the George Coker Mudroom style long box with 2 compartments, the Gilbertson 4 inch PVC plastic pipe box that discourages house sparrows and various experimental models with slot openings.

The most important measurements for box success are the 1 1/2 inch entrance holes to eliminate starlings from entering the box, at least 6 inches from the entrance hole to the floor bottom , interior floor measuring no less than 41/2 x 41/2 inches and an oversize roof that sheds water away from the box. A very important feature is an easy opening door that allows access to the nest and young for monitoring purposes.

A variety of woods can be used for long lasting homemade boxes. I use 1 inch pine barn boards for the sides, inch redwood for doors to repel snoopy Hairy Woodpeckers that want to enlarge the opening and exterior plywood for the roof. Plywood is more stable than solid wood providing weather tight sealing. I have 15-year-old boxes that remain in good shape because they were constructed from exterior grade woods and galvanized hails. Repainting boxes every 3 – 4 years seals and protects the wood. Thicker wood also provides more insulation keeping boxes warmer in spring and cooler in summer.

Nest Box Posts and Predator Controls

The most important step for creating a safe nesting environment for bluebirds is to mount the nest box on a smooth galvanized STEEL POST. I have nearly 500 nest boxes out for everything from wood duck to prothonotary warblers and every one of them is bolted to a galvanized steel pole. In addition to the slippery post, all boxes set up over land are greased heavily. I get old grease from garages and farm auctions. Raccoon like to keep their paws clean so won’t go near a greasy post. Nest boxes mounted over water for wood duck and prothonotary warblers are equipped with a steel cone shaped predator guard or a stovepipe guard. This method will stop any climbing predator and will not pollute the water.

I also use existing predator controls such as high power electric fences surrounding cattle pastures. By pounding the post inches from the wire, a climbing predator cannot avoid getting the shock of its life. I can guarantee from personal experience that one jolt will deter any mammal.
Galvanized posts can be moved to more promising habitats in minutes, last forever with no rusting and don’t allow deer mice to reach the nest boxes for making their winter nests and produce possible Hanta Virus. Steel T Bars are used by many bluebirders but the rough surface enables predators such as deer mice and weasels to gain access to the box.

Starting a Trail

To begin a nest box trail, I would recommend at least 10 nest boxes of at least 2 designs, mounted on galvanized steel posts and set up in an open grassland area over 100 yards from woodlots or bushy areas. These boxes should be set up 80 to 100 yards apart. Bluebirds are territorial and won’t allow another pair within that distance. Position the box so the entrance hole is facing in a southeastern direction. Most winds come from the south and west and the young birds benefit from sunshine early in the day.

Twinning Boxes

Because tree swallow populations have exploded in Ontario, thanks to safe nest box trails, they will compete severely with other nest box competitors. Eastern Bluebird usually arrive earlier to the breeding grounds than tree swallows so the pair have their choice of boxes. The box that the bluebirds are interested in is the one to twin. By adding another box approximately 15 to 20 feet away with the entrance facing the opposite direction of the bluebird’s box will allow tree swallows to nest peacefully. Some trails twin all boxes but this is wasteful and promotes tree swallows to nest side by side. Eventually tree swallows will overcome any bluebirds giving you a "tree swallow trail".

Twinning for house wren predation is more difficult because male house wrens are programmed to make dummy nests and will fill every available box with sticks. When house wrens become a problem, placing a box in or close to wooded bushy area will draw their attention. Hanging boxes from branches are also very attractive to house wrens. House wrens are notorious for spearing or jabbing bluebird eggs with their sharp beaks, usually just before hatching. This destruction is frustrating for the bluebirds and for human landlords as well.


Ontario Eastern Bluebird Society

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