Homeless
Part II: How we can Help Songbirds

GRADES: 5-7

SUBJECTS: Math, Science, Art

OBJECTIVE: Students learn about songbirds' needs and what they can do to help declining populations. They collaborate with their classmates in the care of songbirds.

METHOD: Students will follow specifications for building birdhouses for songbirds in their region.

BACKGROUND

Aside from the aesthetic appeal of having songbirds nesting nearby, there are practical reasons for providing birdhouses. The students have learned about the effects of human-induced habitat loss and degradation on our songbirds. Now here is a chance for them to learn what they can do to help. Extensive habitat loss as described in Activity : Homeless Part I: Songbirds Need Habitat, has created a shortage of suitable nesting sites for native cavity-nesting birds. In some cases, as with bluebirds, this has lead to population declines. Birdhouses provide artificial nest sites for cavity-nesters and can be the key to helping populations recover.

Little expertise is required to build birdhouses; they need not cost a lot and they can be fun to make. This is an ideal project for enthusiastic students. John Lane of Brandon, Manitoba and the children he inspired, put up a string of thousands of bluebird houses across the prairies that has become known as the Bluebird Trail. Bluebird houses were a significant factor in the recovery of the Western Bluebirds' declining population. When the birdhouses are built with thoughtful attention to the specifications provided, not only do the songbirds benefit, but you will be rewarded with a great opportunity to observe and learn about these birds.

Building the Birdhouse

The following table shows the kinds of songbirds that will use birdhouses in British Columbia, and the structures that will attract them. The structure must meet the standards of the particular songbird or it may not be occupied.

Table 1. Sizes for Birdhouses
(Measurements in centimetres except Height Above Ground,
which is in metres)
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In William Carrick's book Nest Boxes for Birds, published by the Canadian Wildlife Service, he describes a useful formula for calculating the dimensions of a birdhouse for a specific kind of bird. The formula is based on the overall length of the bird, a figure available in most field guides. The entrance diameter = 2/3 the length of the bird; one side of a square floor = 2 1/2 X the entrance diameter; the vertical depth = 2 1/2 X the side of the floor.



Wood is the best material for birdhouses. The wood does not have to be finished lumber, rough lumber works just as well. Things like tin cans, coconut shells, gourds, and empty plastic milk cartons have been used with some success. The problems with these materials is that they are often a pre-determined size that cannot be altered and are difficult to clean out or open for observations. Also, the coconut shells and gourds are concave at the bottom which may lead to crowding as the young develop in the nest.

Paint is not necessary, the natural grey of weathered wood seems to be best. If you must paint, use dull, inconspicuous colours and paint the outside of the box only. If light-coloured plastic jugs are used, it is best to coat the outside with dark paint since cavity-nesting birds like dark interiors.

Although the design of the birdhouse will depend on the species of bird you wish to attract, there are some features which are common to all. The birdhouse must be durable and as weather-proof as design permits; it must be properly ventilated; have a removable roof or side for cleaning and for checking the contents; and it should have a sloping roof and holes in the floor for drainage. The proper floor area is important to ensure enough room to accommodate the nest, the eggs, or young, and the incubating bird.


When and Where?

Once the birdhouse is built, it is up to the students to choose an appropriate spot for the house and to ensure that it is put up during the proper time to keep unwanted guests (House Sparrows and Starlings) out. Bird houses should be put up just prior to the arrival of the species you are building it for to reduce the chances that the house will be occupied by unwanted species. If the house is already in place from the previous year the hole can be stuffed with paper or covered with plastic until the arrival of the desired species.





The table that follows gives arrival times for some of our songbirds.

Table 2. Spring Arrival Dates for Some Songbirds in British Columbia
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Another way to deter unwanted bird species is by the design of the house. To discourage Starlings from occupying a swallow house make the hole oval (4 X 3 cm) instead of round. To deter House Sparrows do not put a perch at the entrance hole.

To avoid mammalian threats - raccoons, cats, squirrels and rats - location is important. If the house can be reached, either along a limb of a tree, up a pole, or over the roof of a garage, then it can be reached by one of these predators. Houses on poles or in trees can be protected by metal sheeting, (a piece of stove pipe works well) around the trunk or pole, at a suitable height above the ground. Houses hung on eaves are particularly vulnerable unless out of reach of predators. If your eaves are wide, the house can be hung under them, against the wall of your home and out of reach. Keep in mind that many cavity nesters such as Tree Swallows, Violet-green Swallows, Purple Martins and bluebirds, will not use houses nestled among trees, because they like to be out in the open. Also, remember that most birds don't like close neighbours of their own kind.

Maintenance

The house needs to be cleaned annually, usually in spring before the new nesting season begins. All old nesting material should be removed and burned to kill any insect eggs or larvae it contains. The house should be left open for a few days to air out. Cleaning is important because the nests of birds are occupied by many other living things, most of them detrimental to birds. For example, nests have been found with more than 2 300 parasites living in them. These parasites were all indirectly or directly dependent on the nestlings. They are one of the most common causes of death in nestlings and can only be controlled with efficient maintenance.

MATERIALS

• Wood (about 2 cm thick)
• Building tools: saw, nails, hammer, etc.

PROCEDURE

1. Discuss with the students how birdhouses can help provide nesting sites for songbirds that are threatened with habitat loss, as they learned in Activity : Homeless Part I: Songbirds Need Habitat.

2. Identify the songbirds in your region that will use birdhouses from Table 1 above. Divide the students in groups of 2 to 4. Have them build the birdhouses according to the specifications of their choice. They can also do further research on essential design features of birdhouses.

The following is an example of good design features for a Western Bluebird birdhouse that can be adapted to fit other songbirds' needs as well:

• Use wood that is at least 2 cm thick. This provides insulation from the heat of the sun.
  
  
• The roof should overhang the entrance hole by at least 3-5 cm to keep the rain and sun out.
  
  
• No perch - this will discourage House Sparrows.
  
  
• Drill a few small holes in the sides or back, or leave gaps between the sides and roof for ventilation.
  
  
• The houses can be nailed to a post or tree. They should be at least
  200 m apart. Make sure they are in areas of short vegetation and where there are overhead wires or branches for perches and trees for sheltering their fledglings.
  
  
• Drill holes in the bottom or leave space between the floor and the sides for drainage.
  
  
• One of the sides or the top of the box should be hinged or removable so that the house can be cleaned easily.

3. Discuss the importance of accessibility and maintenance of the birdhouse. Further research on the songbird that they have built a house for will help the students locate its preferred habitat.

4. Hang the birdhouses in suitable locations according to the students' research. The groups should monitor their birdhouses. They should identify and report any residents to the class through a few, carefully timed visits, so they do not to disturb the occupants too much. Important information to record includes: when the birds first showed interest in the house, when they began nest building, when and how many eggs were laid and hatched, what foods were brought to the young and when the young left the nest.

EXTENSIONS

There are many songbirds with declining populations that do not use birdhouses. Helping these birds is usually more complicated than simply offering a nesting site. It often involves helping to restore lost habitat. Find out if there are any habitat restoration, enhancement or preservation projects going on in your community and get the students involved.