BIRD OVER THE TOP

We often think that the environment around us is held in some sort of "balance" but in reality, the environment is always changing. The animals we see alive today have been those that have adapted to the change. We hear so much about birds that are perilously in decline but for some species, the situation is quite the opposite. Bald eagles, ospreys and many other birds of prey suffered through the 1960s and 1970s from some industrial contaminants. The most infamous was DDT which caused widespread egg shell thinning among especially birds of prey. The numbers of bald eagles declined in the lower 48 United States to a point that it joined the unenviable endangered species list. However, with the banning of DDT and other problem chemicals, the numbers of birds of prey appear to be on the increase. Eagles and ospreys are making a comeback in British Columbia, northern California, the Great Lakes, the eastern seaboard and in Florida. And it was removed from the Endangered Species list a few years ago. We don't have the data to state unequivocally that the recent increase in British Columbia is a consequence of the ban but increases are very apparent. In the 1970s there were about 65 pairs of nesting eagles in the Gulf Islands and by 1986 the numbers had reached about 120 pairs.

The European starling is a celebrated introduced species that spread quickly across the North American continent following the release of a few birds in New York state about a century ago. The crested myna that was released in Vancouver about the same time did not expand much beyond southern British Columbia. The reason that the myna failed to expand whereas the starling was immensely successful is a simple physiological one - the myna incubates its eggs less attentively and therefore hatches fewer eggs than the starling. Today the starling's invasion appears to be waning near the outer edge of its range for unknown reasons. In eastern North America, the house finch has quickly expanded in response to people providing them with food at bird feeders. There have been some natural invasions to North America in recent years. The cattle egret arrived by flying across the Atlantic early this century. It has become well established in the United States.

If you want to know how birds are doing in North America, point your browser to the Patuxent Wildlife Research Center site. (This link will take you to an external site, so make sure to bookmark this page before you leave!)

back to Butler on Birds homepage