Removing dry and damaged trees from forests, parks and orchards is very unfavorable cavities. Sometimes they manage to find a shallow hole in the tree and lay eggs there, but in such cases chicks are likely to fall out and die on the ground or become an easy prey to various predators.
By setting up nestboxes, or birdhouses, we can help a number of birds which have trouble finding a good nesting place. Birdhouses are a great substitute for natural holes in trees, and there are over 60 different bird species that use them, including the blue, great and coal tit, nuthatch, sparrow, starling, spotted flycatcher, robin, common kestrel, scops owl and tawny owl.
It is best to make birdhouses of 2-2.5 cm thick boards – metal and plastic should never be used for this purpose, because they do not provide any thermal insulation.
The roof should be made of hard wood, resistant to moisture and drying or covered with a piece of rubber or similar material. In order to ensure the drainage, a couple of 6-7 mm holes should be drilled at the bottom of the birdhouse.
The size of the entry hole depends on the bird species for which the birdhouse is made, and varies from 2 cm for tits, to 15 for tawny owls. The hole must be at least 10 cm above the bottom of the house, to prevent the nestlings to fall out or be caught by a predator. The inner sides of the birdhouse should be rough, so that the birds can easily climb to the opening when the time comes for them to leave the nest. If the material for building birdhouse is smooth, several shallow cuttings should be made on the side facing the inside of the birdhouse using the saw.
In order to ensure the durability, birdhouses can be painted with bird-friendly, water-based wood-protection products, but only on the outside. It is important to avoid painting the birdhouses with bright colors. The birdhouses should be cleaned regularly -they need to be assembled in a way that the roof, bottom or sides can be easily removed.
It is best to place the birdhouse 2-5 m above ground, out of reach of cats and curious people, turned so that the entrance is sheltered from direct sun and prevailing winds. In order to prevent the rainwater from entering, the birdhouse should be slightly tilted forward, and a 3-5 cm layer of sawdust should be put inside the birdhouse before setting it up, in order to prevent rolling and breaking the eggs.
Bird houses should be set up before the breeding season, preferably between September and March, so that the birds would have enough time to inhabit them. Most birds nesting in cavities are territorial species, so the birdhouses should be placed 20-40 m away from each other.
Some birdhouses are used throughout the year – not just for nesting, but also for shelter during autumn and winter, but it can still take several years before the birds find and accept them.
Most birds are very sensitive to disturbances during the nesting period – some of them can even leave the nest, eggs or nestlings. Therefore, we shouldn’t disturb them during spring and summer, but enjoy watching them from a considerable distance.