30% of wild birds have disappeared from the North American sky. Research teams such as Cornell University in the United States have examined the number of birds in North America over the past 50 years and have announced an estimate that it has decreased by about 3 billion birds. Birds are said to be a barometer of environmental health. A worldwide decline in birds has been reported, revealing that the ecosystem is threatened.
The research team analyzes data on wild bird surveys in North America and migratory bird data reflected in weather radar, which are made annually in cooperation with citizen volunteers. We examined 529 species, 90% of the birds that live in North America. As a result, it was estimated that since 1970, the total number decreased by 29%, or about 3 billion.
Ninety percent of these were birds familiar to sparrows such as finch, mussels and swallows. They play a role in eating pests and spreading plant seeds. Also, the number of seaside birds has already decreased by 30%. Spring migratory birds have decreased by 14% over the last decade.
Although the research team has not analyzed the cause of the decline, other studies have reported that the number of birds has declined due to an increase in farmland and urbanization worldwide. In addition to cats walking outdoors, collisions with windows and buildings, the use of pesticides, changes in the environment due to global warming have been pointed out.
On the other hand, water birds such as ducks and swans, and raptors such as the national bird bald eagle in the United States are said to have recovered in number due to conservation activities and the prohibition of pesticides such as DDT.
The American Bird Conservation Society who participated in the research ...