By the end of the century one in 10 species of birds in the world will be extinct and a further 15 per cent will be on the brink of extinction according to one of the largest studies of avian biodiversity.
The dire state of birds is documented in an American university study which shows their decline will accelerate rapidly in a world of habitat loss, disease, climate change and over-exploitation.
It is estimated that just over 1 per cent of bird species have become extinct in the past 500 years but this is set to increase tenfold over the next 100 years, according to a study led by Cagan Sekercioglu of Stanford University in California.
The researchers found that the loss of birds will not only have an impact on other wildlife but could also increase the risk of epidemic diseases hitting the human population.
They cite the recent decline of three species of Indian vulture, caused by the widespread use of a veterinary drug by local cattle farmers. The decline led to an explosion in the population of feral dogs feeding off dead cows, leading to 30,000 cases of human rabies a year.
"Our projections indicate that, by 2100, up to 14 per cent of all bird species may be extinct and that as many as one out of four may be functionally extinct, that is critically endangered or extinct in the wild," Dr Sekercioglu said. "Even though only 1.3 per cent of bird species have gone extinct since 1500, the global number of individual birds is estimated to have experienced a 20 to 25 per cent reduction during the same period," he said.
"Given the momentum of climate change, widespread habitat loss and increasing numbers of invasive species, avian declines and extinctions are predicted to continue unabated in the near future," he added.
The study involved analysis of all 9,787 species of birds alive today, and of the 129 species that have gone extinct recently, to produce one of the most comprehensive databases ever compiled into the state of one class of animals.
Using a computer forecast based on current rates of decline, the researchers found overall that just over one in four bird species is currently prone to extinction and 6.5 per cent are "functionally extinct", meaning they no longer play a meaningful role in the local ecology.
A quarter of fruit-eating birds and omnivorous species are in danger of becoming extinct, along with a third of herbivorous, fish-eating and scavenging species.
In the worst-case scenario put forward in the study published today in the journal Proceedings of the National Academy of Sciences, the researchers predict that threatened bird species will increase by 1 per cent each decade.
"These assumptions are conservative, since it is estimated that every year natural habitats and dependent vertebrate populations decrease by an average of 1.1 per cent," says the study.
Gretchen Daily, a member of the research team, said it may be difficult to imagine how the loss of a particular species of bird can cause an outbreak of human disease. "Yet consider the case of the passenger pigeon. Its loss is thought to have made Lyme's disease the huge problem it is today.
"When passenger pigeons were abundant and they used to occur in unimaginably large flocks of hundreds of millions of birds, the acorns on which they specialised would have been too scarce to support the large populations of deer mice, the main reservoir of Lyme's disease, that thrive on them today," said Professor Daily.
© 2004 Independent Digital (UK) Ltd