Fully one-third of all North American bird species need quick help to stop them from disappearing, says the first continent-wide bird study conducted jointly by Canada, the United States and Mexico.

Of the 1,154 species of birds that fill the forests, marshes, coastlines and grasslands from the Yucatan peninsula to Baffin Island, 432 of them are considered at high risk of vanishing from the skies forever, according to the North American Bird Conservation Initiative.

"This is a continuation of trends we've known from national reports in the not-too-distant past," said Steven Price of Bird Studies Canada, one of more than a dozen non-profit groups also involved in the study.

Worst off are seabirds. The report found seabird populations have declined by nearly three-quarters since the 1950s and that 57 per cent of those species are on the road to extinction without conservation action.

Tropical and subtropical species are almost as bad off. And the report adds that between one-quarter and one-third of species along coasts, on the prairies or in drylands are going the way of the dodo.

Even in the boreal forest, the vast swath of green along the northern ends of the provinces, about 20 per cent of all species are in danger of dying out.

Only two groups of birds are increasing, says the report. That's because waterfowl such as ducks and geese and raptors such as peregrine falcons already benefit from conservation actions.

"We spent money and changed policies and these birds have recovered," Stevens said.

The culprits behind the losses are familiar. Habitat chewed up by homes, farms or industry is a major contributor. So is pollution. Climate change alters once-familiar homes quicker than birds can adjust.

The results have been echoed in previous studies.

A 2014 study by the Audubon Society found climate change could cost 126 species more than half their current range by 2050. A McGill University study in 2015 concluded more than 70 per cent of global forests are within a kilometre of a road, field, town or other human disturbance -- easily close enough to degrade forest habitat.

Nature Canada, another group involved in the study, called for more than $80 million for research and conservation as well as the creation of national wildlife areas and marine conservation areas. The group also wants Ottawa to stop the province of Saskatchewan's plan to sell or lease community pastures.

The three national governments are expected to sign a letter of intent Wednesday to work more closely together to protect birds on a continental scale.

"The solutions require international collaboration," said Charles Francis of the Canadian Wildlife Service, who co-ordinated the bird report.

Francis said the letter commits the countries to work together to protect bird populations shared by all three while allowing local people to earn a living on the landscape. The document won't be immediately accompanied by any funding or specific policy goals but will set the stage, Francis said.

"It gives focus to the staff within Environment Canada to spend greater effort on continuing to work internationally."

Some groups have called for half of Canada's boreal forest to come under some kind of protection. Quebec and Ontario have agreed to try to meet that goal.