The researchers calculate that there are now 421 million fewer birds across 25 European countries than there were at the start of the 1980s — a change the study attributes to human-caused environmental degradation.
The scale of decline, in the words of the study just out in the journal Ecology Letters, is “alarming.” The research finds that out of the 144 most common species, there were about 2.06 billion birds in Europe in 1980, and just 1.64 billion in 2009 (the last year considered in the study). Thus, the loss of 421 million represents more than a 20 percent decrease.
“90 percent of that decline can be attributed to the 36 most common species,” says lead study author Richard Inger, from the University of Exeter’s Environment and Sustainability Institute. According to Inger, the top five species experiencing stark declines are the house sparrow, the common starling, the Eurasian skylark, the willow warbler, and the Eurasian tree sparrow.