By Cliff Bennett
Photo: Christine Taylor
This past winter, several members of the Mississippi Valley Field Naturalists (MVFN), situated in the northern half of Lanark County in Eastern Ontario, spent a cold wintry Saturday building bluebird boxes. They hope to establish a bluebird trail in the area this spring. The plight of the Eastern Bluebird has long been of interest to naturalists across North America, ever since the 1950s when man almost wiped them out with DDT. Another single deterrent to the successful nesting of these beautiful songsters was the introduction of the European Starling to our continent, a species that spread prolifically a century ago and assumed the bluebird’s natural nesting cavities. Building bluebird boxes and establishing nesting trails has been a constant quest ever since.
Planning to establish a bluebird trail begins in the winter, and installing boxes should happen ideally in March in order to capture the attention of this year’s crop. Here are some tips for a successful venture:
- A box design called the Peterson Oval has proven to be a very effective nesting platform for the Eastern Bluebird.
- Untreated wood is safest for the birds. As for painting, the box will be less conspicuous to predators if left unpainted. If you do paint, however, use natural colours with a matte finish and be sure not to paint the inside, where fumes and flakes may harm the birds.
- Locate boxes in open grassy areas with scattered trees for perches. Cemeteries, pastures, golf courses, areas surrounding old apple trees and large yards are ideal. Bluebirds are essentially insect eaters, but they also enjoy small fruits from vines and bushes.
- Place your boxes 100 metres from buildings to prevent house sparrow problems and 40 metres from bushy areas to prevent house wren competition. Placing boxes in pairs, three metres apart, will also deter tree swallows. The swallows will take over one box but fight off any other swallow interlopers close by. They don’t mind being next to bluebirds.
- Mount the boxes on a metal post or a post with a piece of 12.7 cm metal furnace duct pipe over it. These are the best deterrents against predator animals. The box entrance should ideally be 1.5 metres from the ground and face south to protect from northerly winds.
- Plan to check your boxes regularly. It’s vital to keep house sparrows away and also to look for other predators and interlopers.
- Check each box regularly for parasites, especially blowfly larvae. To do this, lift the nest with a spatula. Better still, install a hardware cloth floor about 2.5 centimetres from the bottom of your box, so the larvae will fall through the holes. Clean out your boxes in the spring before the bluebirds return home.
- Keep a record of your weekly visits. Build a data bank on the successes (and failures) of your venture.
- If you haven't the space for your own trail, ask a farmer or other land owner for permission to establish one on their property. Be sure to share the results with the landowner. Better still, get the landowner involved in monitoring and maintenance.
- Involve children's groups in your trail program. They are tomorrow's guardians of these delicate insect eaters.
Keeping track of your bluebird boxes is often a challenge. Just when you think all is well, the birds are suddenly not there. The problem could be one of many, so here is a list of situations, their likely cause and what you can do about it:
- The box is filling up with unorganized sticks, sometimes even on top of the bluebird eggs; the eggs are pierced and/or on the ground underneath the box, leaving the nest undisturbed; or the chicks have head injuries or are dead and on the ground.
The likely cause of these problems is the house wren, and the solution is to keep the twigs away, plug the hole until the wrens go away, move the bluebird box away from shrubs, build and locate a wren box near the same shrubs or let the wrens have the bluebird box (the damage is already done), and locate a new bluebird box away from the wren nest.
- Same problem as above, but the box is filling up with grass, straw and other trash. Also, the adult bluebird may be dead in the nest with its head pecked.
The villain here is probably the house sparrow. The best thing you can do is place the bluebird box somewhere else, far away from the sparrow’s source of food.
- White feathers are on top of the nest, even covering the bluebird eggs. Everything else is undisturbed.
Tree swallows cause this issue. The solution is to place another box about one metre away from the first one. The swallows don't mind bluebirds around but will drive other swallows away. They will also fight off sparrows and wrens, thus defending their own box and the bluebirds’.
- The birds and eggs are gone; the nest is pulled apart or out of the hole and there are scratch marks on the box.
The enemy here is a cat or raccoon. Clean out the box, relocate it to a metal pole with a predator baffle or pipe attached. Be sure the box is away from bushes and buildings.
- All eggs and birds are gone, but the nest is not disturbed and there are no scratches on the box.
The predator is probably a rat or bull snake. As an after-the-fact solution, move the nest to another location and install a predator baffle.
- One or more eggs or young are missing, but the nest is undisturbed.
A blue jay, crow or grackle often causes this problem. To prevent the predator’s head from entering the nest box, place a thick predator guard around the hole. If the nest is too close to the hole, remove half of the debris from under it to the effect of lowering the nest edge.
- The adults are fluttering about outside the box but don't go in.
The trouble here might be wasps or a bumblebee inside. Check the inside of the lid for a bees' nest. If there is one present, wait until evening when it is cooler and the bees are docile to scrape the eggs away, but not into the bottom of the box. Rub bar or liquid soap on the lid inside to repel these pesky insects.
- The nest is infested with ants.
This problem indicates there is something to feed on, probably old eggshells or dead nestlings. Clean out the box and replace the nesting material. Apply a band of grease or Vaseline around the pole.
- The nestlings are weak and slow to develop, and their wings and heads are scabby. The nest is damp and smelly underneath the cup, and brown pupae capsules are in the bottom of the box.
This problem is caused by the blowfly larvae. The solution is to remove the nestlings, pitch the nest and thoroughly clean the box. Pack the inside with dry grass and return the nestlings. Do not use insecticides or other chemicals. However, if the babies are more than 13 days old, do nothing; they will probably survive.
Helping to maintain a healthy Eastern Bluebird population is a noble venture. Anyone involved in this activity should be congratulated.
Cliff is a founding member of the Mississippi Valley Field Naturalists and a columnist on birds for the Lanark ERA.