The number of Adélie penguins living in East Antarctica may be double what scientists previously thought.

New data collected by researchers at the University of Adelaide in Australia estimates the population number at nearly six million—almost four million higher than previous estimates.

Until this most recent study, scientists drew their estimates by counting breeding pairs. However, this means previous counts missed non-breeding penguins.

“Non-breeding birds are harder to count because they are out foraging at sea, rather than nesting in colonies on land,” Louise Emmerson, a seabird ecologist with the Australian Antarctic Division, says in a press release.

Using a combination of aerial and ground surveys, as well as automated camera images, researchers were able to collect more accurate population counts over several breeding seasons and revise their estimated totals.

Crowded Shores

Higher numbers are a cause for celebration and concern. Adélie penguin colonies span the entire Antarctic continent, and the birds stay mostly on land during the Antarctic summer, between October and February, to nest and breed. During this time, adults may have to walk up to 30 miles to reach the sea and hunt for fish and krill.

Given the new population count, this behavior suggests that more penguins may be interacting with people than previously thought.

Adélie penguins prefer to nest in rocky areas that are free of ice, and those are the same areas where researchers prefer to set up camp so they have easier access to resupply ships, says seabird ecologist and lead study author Colin Southwell.

According to Southwell, more than a million birds breed within just 12 miles of a research station.

“By identifying significant penguin breeding populations near stations, we can better identify which areas may need enhanced protection into the future,” Southwell says.

Boom to Bust

And while the revised Adélie penguin numbers may seem high, the seabirds are facing significant threats.

Antarctica is particularly vulnerable to the effects of climate change. Shifting ice and melting glaciers may reduce viable habitat for the birds, while warming ocean waters could affect the availability of their prey.

Warming on Antarctica can also lead to rainfall or premature ice melt during breeding season, causing puddles to form. These puddles can cause hypothermia for young chicks that become wet before they are able to develop waterproof feathers.

Research published last year by the University of Delaware found that more than half of the current Adélie habitat could be unsuitable for penguin colonies by the end of the century.

In a 2015 interview, Southwell said that receding sea ice could potentially help the eastern penguins access more krill and fish, causing their already healthy numbers to boom. But he cautioned that this could be more detrimental than beneficial over the long term.

"The rationale is that any creature—including humans—can have too much of a good thing," he told ABC News.

And Adélies elsewhere in Antarctica have not been faring as well. Palmer Station, a U.S. research hub in the northern region of the continent, saw nearby populations decline by 80 percent over a 30-year period.