Ontario Eastern Bluebird Society

Monitoring Nest Boxes

Male Eastern Bluebird feeding mealworms to young.

- Photo by John Millman

When bluebirds begin to use nest boxes, the trail operator is responsible for insuring the success of the nesting by carefully monitoring the box. You must be prepared to solve any problems that may arise.

Eastern Bluebird incubation usually takes 14 days. It is important to know how many eggs are in the nest but females should not be disturbed too often at this stage. When she is incubating, a quick whistle of their call will cause her to peek out of the entrance. The male will also be present nearby if everything is normal. If the nest material is thin, extra dry grass under the nest will provide more insulation to the eggs. Keep a record of white eggs or discoloured blue eggs.

After 14 days, the fun part of monitoring begins. Bluebirds will allow the opening of boxes for a quick observation of the young without abandoning them. Accurate records must be kept at this point including number of young hatched and date of hatching. This is very important for later nest failure or orphaned young. Anything is possible from hatching to fledged young. If the weather is warm and there is abundant insect food available, monitoring is a very enjoyable experience. If the weather is cold and damp, you can expect to find dead young, cold abandoned young that can hopefully be fostered in other boxes or even dead adults right in the box with their young. Young bluebirds fledge from 18 21 days so it is important to know how old they are to prevent premature exiting of the box. Boxes should not opened after the young reach 14 days. If one jumps out, it is very difficult to return it safely.

Other problems beside weather could be climbing or flying predators, lack of water in summer broods, box vandalism or careless tractor operators and always competition for nest boxes by aggressive tree swallows or house wrens. Check the trouble-shooting chart for solutions to most problems. It is also a good idea to carry any tools needed for opening boxes or adding and adjusting predator guards, a bag of dry grass to increase the nest thickness especially after blowfly larvae have been removed and a can of grease to apply a thick coat on the slippery steel post.

The beginner trail operator should set out only the number of nest boxes that can be easily monitored. Keep your trail close to home and find out the location of other nest boxes nearby in case of emergency.

Bluebird trails can be demanding and frustrating but the rewards are great.


Ontario Eastern Bluebird Society

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