Beauty of Earth

Almost one third of the 800 species of birds found in the US are "endangered, threatened or in significant decline", a report has concluded.

Described as the most comprehensive assessment of its kind, the study listed habitat loss and invasive species as being the main threats.

But where conservation measures had been taken, some bird populations had shown signs of recovery, it added.

The US State of Birds report was commissioned by President Bush in 2007.

It was compiled by a partnership of organisations, including the US Geological Survey and the American Bird Conservancy, from three long-running bird censuses stretching back 40 years.

Habitat concerns

"Habitats such as those in Hawaii are on the verge of losing entire suites of unique bird species," warned David Pashley, American Bird Conservancy's vice president.

As a result of the encroachment of human activities, nearly all of the bird species on the Hawaiian Islands were in danger of extinction unless urgent conservation measures were implemented.

"In addition to habitat loss, birds also face many other man-made threats, such as pesticides, predation by cats, and collisions with windows, towers and buildings," Dr Pashley added.

The report also found that at least 39% of ocean bird species were declining, and about half were of "conservation concern".

It also highlighted that half of coastal migrating shorebirds had declined, "indicating stress in coastal habitats besieged by development, disturbance and dwindling food supplies".

The researchers said it indicated deteriorating conditions and that effective "management policies and sustainable fishing regulations were essential".

But the report also presented evidence that populations of birds recovered quickly when conservation measures were taken.

The data revealed "dramatic increases" in wetlands species, such as pelicans, herons, egrets, ospreys and ducks.

"These results emphasise that investment in wetlands conservation has paid huge dividends," observed Kenneth Rosenberg, director of conservation science at the Cornell Laboratory of Ornithology.

"Now we need to invest similarly in other neglected habitats where birds are undergoing the steepest declines."