Once on the brink of extinction, whooping cranes are continuing their long, slow recovery.

Using a helicopter to comb 4,000 to 5,000 square kilometres of land, biologists in Wood Buffalo National Park spotted 202 birds with a total of 32 young fledglings during an annual summer survey — up from 28 fledglings last year.

Stuart McMIllan, a biologist at the park, says the young ones are difficult to spot.

“The fledglings are kind of a tan colour; they haven't developed their plumage yet,” he says. “So sometimes when you're doing the surveys it's easier to pick out the pairs from the air, and extra effort to find the chick because it may be hiding in the tall grass.”

If that’s not enough, more and more birds are nesting outside of the park in the Northwest Territories.

“As they do that, it takes a bit more effort to look beyond their traditional core nesting area to find them,” McMillan says.

The whooping crane is the biggest bird in North America. The adults are white and stand up to 1.5 metres with a wingspan of up to 2.4 metres.

McMillan says even though the cranes are still listed as endangered, the results are encouraging.

“Over the last ten or twenty years they've shown a nice increase in numbers,” he says.

“The whooping crane is certainly that iconic story of recovery.”

Survey an annual event

Each year, park staff team up with the Canadian Wildlife Service — a branch of Environment Canada — to do two aerial surveys of the cranes' nesting grounds.

A nesting survey is done in the spring, followed by a fledgling count in August.

In 2013, the survey team spotted 74 nests in the spring and 28 fledglings later in the summer.

This year, they saw a record of 82 nests from the helicopter and in August, saw 32 fledglings.

"That gives a success rate of about 40% when compared to how many fledglings we have when compared with the number of nests they started out with in the spring," McMillan says.

In all, park biologists saw 28 pairs with one chick, and two families with two chicks.

McMillan says the cranes will start to migrate to their winter grounds on the Gulf of Mexico in Texas over the next couple of months.