People often have prejudices about various animals, deciding that they do not like something because of some behaviour they perceive in that animal. I must, in honesty, admit to having a prejudice myself regarding the House Wren. This perky, cheerful sounding little bird can raise havoc on nest box trails, by piercing the eggs of the bluebirds and swallows, and sometimes killing the adults. However, I am able to work around this by recognizing that the wren has a right to live, the same as any other native bird. I can deal with the destructive habits of the wren by using its other habits to minimize the darker aspects of its behaviour.

Let's look at a species that many bird-lovers hate, the American Kestrel, a small falcon about the size of a robin. This neat little falcon was formerly called the Sparrow Hawk, because it sometimes will take a small bird for its lunch. This somewhat rare behaviour has infuriated some people for years, and many kestrels have paid a heavy price. The largest part of the diet of the American Kestrel is insects, such as grasshoppers, and small rodents make up the next largest part. Only a very small percentage of the diet is songbirds, but this plays a part in the natural selection process in those birds. The strong and smart ones will survive to raise young, while the weak and stupid will be kestrel food. The whole idea of hating some animal because it eats some other animal, or because of the way it finds food for itself and its young is not very bright! Nature has evolved the behaviours and physical attributes of animals (and plants) to maximize the survival rates of each species.

Where there is a niche in an environment which provides the food and shelter for a particular species, that species will expand to fill the niche. When there is a change in the environment, some niches will disappear and others will open, so there will be a loss of some species populations and a gain in others. When we humans make a change in the local environment, nature will adjust the balance of species in that environment. If we provide artificial cavities for some birds that used to nest in woodpecker holes, and there is a food source in the insect population, those birds will nest and breed in that area, reducing the insect population. This reduction will, in turn, limit the population of insect eaters, balancing the bird population with the food supply. If the insects that are eaten would have eaten desirable plants, we humans count this as a success. If the insects were ones which benefit man, (not too likely) then we would probably say that the process was a disaster.

The provision of nest boxes for the cavity nesters is not a new change to the environment, but a return to a more normal state. We humans seem to like having everything neat and tidy in our world, so we clean up and burn all of the old dead trees in our wooded areas, which reduces the woodpecker population which depended on those old dead trees for food and nest sites. This reduces the populations of secondary cavity nesters, such as bluebirds, small owls, tree swallows, and some ducks which use woodpecker holes for nests. When we provide nest boxes, we only return our bit of the world to a more natural state. In general though, when we make changes in nature, we must watch where we step, as there could be some nasty things pop up which we would hate to have on our shoes!

Carl Grosfield
5105-51 Ave.
Vegreville, AB
T9C 1M1
wildscape@telusplanet.net