One in eight bird species worldwide faces the threat of extinction, according to a report released by Birdlife International.

And it isn't just rare birds that are declining. Familiar species such as the barn swallow and purple martin are disappearing at an astonishing rate. In the case of those two birds, 80 to 90 per cent of the population was wiped out in the last 20 years.

"Unless we take action now to improve their fortunes, these are species that are going to go extinct in the coming years," argues Stuart Butchart, Birdlife International's chief scientist.

The main culprits are unsustainable agriculture and climate change.

For example, vast swaths of tropical forests in Southeast Asia and Africa are being cut down and replanted with oil palms. The new monoculture is a gut punch for biodiversity.

According to a Birdlife International study, one in eight of the world's bird species are threatened with extinction. (Birdlife International)

"Natural habitats are being converted and many, many species are losing large parts of their population and their range," says Butchart.

With climate change the warming temperatures prompt earlier migrations and nesting. This often puts birds that travel vast distances out of sync with the insects that make up their diets.

"The butterflies, the caterpillars are emerging at a different time to when the adults need to find their food to feed their chicks," says Butchart.

The report released Thursday is being unveiled at Birdlife International's 2013 Congress in Ottawa and draws on the knowledge of more than 120 affiliated national bird organizations.

Canada's bird population is faring well when compared with the rest of the world, but that isn't saying much.

Overall the Canadian bird population has declined about 12 per cent in the last 40 years, according to Ted Cheskey from Nature Canada, one of Birdlife International's two Canadian partners along with Bird Studies Canada.

Four out of five Canadian bird species spend part of their lives outside of Canada. Migratory birds are in the steepest decline.

Cheskey said there are three Canadian bird populations — most migratory but some not — that are of concern:

Insectivores (e.g., barn swallows and purple martins).

Shore birds (e.g., the piping plover).

Grassland birds (e.g., the sage grouse).

"If we lose them, it takes a piece of our biodiversity away and it has a ripple effect throughout the ecosystem as well," says Cheskey.

On the plus side, many Canadian bird populations have rebounded. With the elimination of DDT as an insecticide, raptors such as the peregrine falcon are making a comeback, says Cheskey.

The Philippine eagle, also known as the monkey-eating eagle, is the national bird of the Philippines and is critically endangered. Killing one is punishable under Philippine law by 12 years in jail. (Nigel Voaden/worldsrarestbirds.com)

Although the Birdlife report is about birds, Cheskey and Butchart both say it opens a window on the rest of the natural world.

"Birds are fantastic indicators. They are good at telling us where other wildlife is found and their trends also closely mirror what's happening to other wildlife groups. So the fact that many bird species are declining, many are threatened with extinction, really should be ringing alarm bells," argues Butchart.

Both men say that if governments and citizens want to do something to protect birds, they should begin to legislate protection for Important Bird Areas. IBAs are sites identified around the world by Birdlife International that are critical habitats for the survival of birds.

But protection does not necessarily mean the elimination of all human interference. For instance, IBAs can also be important hunting grounds for aboriginal cultures such as those in James Bay.

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"We want them to be places where people can sustain their own livelihood. That's a very important theme with Birdlife," said Cheskey.

As for the future of the world's avian population, Cheskey has mixed feelings.

"There's days when I'm worried and there's days when I have a lot of hope. Fortunately, meeting people that have hopeful stories of little changes they can make, they certainly keep me going."