A naturalist says bird populations can be an effective measurement of the state of the environment in the last 50 years, which makes monitoring programs all the more valuable.

"The insects these birds eat are in decline and, as a result, these birds are in decline and in trouble," Jim Critchley told CBC News.

"That is in part because of climate change and in part because of human activity."

Naturalist Jim Critchley is part of a bird box monitoring project at Leighton Art Centre near Millarville, Alta. (Audrey Neveu/Radio-Canada)

Critchley is a naturalist, citizen scientist and board member at Leighton Art Centre, where he's been part of a nesting box program that monitors bird populations since 2016.

The centre is about 25 kilometres southwest of Calgary, near Millarville.

"Data has been collected since the 1970s and the graph just shows a dramatic decline. The trend is downward and the populations of these birds is downward," he said.

One of the bird boxes at the Priddis Greens Golf & Country Club. (Karen Rice)

The North American Bird Conservation Initiative (NABCI) monitors trends in bird populations.

The 2019 State of Canada's Birds report published by Environment and Climate Change Canada states while some populations are recovering or in a state of little to moderate change, shorebirds, grassland birds and aerial insectivores (like swallows) are "rapidly declining" requiring "urgent conservation action."

"Canada has lost 40 to 60 per cent of shorebird, grassland bird, and aerial insectivore populations. In the last decade, 80 per cent of bird species newly assessed as threatened or endangered in Canada have been aerial insectivores or grassland birds," the report notes.

Eggs inside a bird box at the Priddis Greens Golf & Country Club. (Karen Rice)

Boxes strategically relocated 3 years ago

About 35 years ago, 20 bird boxes were set up at the Leighton Art Centre, but they were put far too close together, so three years ago Critchley was part of a redistribution project that spread 14 boxes strategically across the 80 acres of the property.

The project also monitors more than 100 boxes at the nearby Priddis Greens Golf & Country Club.

He says they are targeting two species that are at risk and need human help to survive: the mountain bluebird and tree swallow.

"They are almost totally dependent on humans to build nest boxes for their survival, because of invasive species like European starling and house sparrow," Critchley said.

Those invasive species along with wrens, magpies, crows, ravens and weasels have made it challenging for the mountain bluebird and tree swallow.

Chicks born as part of the bird box monitoring program. (Karen Rice)

That's where the monitoring program comes in.

"It's really important that we do what we can to actually create habitat for them so that they can survive and nest and reproduce," he said.

So checking on the boxes, tagging birds and keeping the holes on the boxes small enough to prevent bigger birds from getting in are all steps in the right direction, Critchley said.

While this specific program has been a success, he says insects in the province as a whole are down, therefore the bird populations are also in decline.

A bird after being tagged as part of a monitoring program at the Priddis Greens Golf & Country Club. (Jamie Bussey/Submitted by Jim Critchley)

Insects are Tonya Mousseau's specialty. As an entomologist and professor at Mount Royal University, she says some insects have been on the decline for a while.

"Forty to 50 per cent of insect species, worldwide, are in decline, some groups more than others," Mousseau said.

Climate change is one of the factors.

A bird is released at the Priddis Greens Golf & Country Club after being tagged to monitor its progress. (Jamie Bussey/Submitted by Jim Critchley)

"Mostly habitat loss is what we have been able to document so far, but there are lots of other factors like climate change, pollution, pesticides, loss of food for the insects," she said.

"We are trying to figure that out right now."

'Important to take note'

"Birds are very sensitive to changes in the environment. Part of this program is about closely watching bird populations. When there are subtle, detrimental changes in the environment, bird populations change. Their numbers go down," Critchley said.

"When we see a decline in the number of birds, we are really telling the story of the environment we are living in. It is important to take note."