A team of Canadian scientists may have cracked one of the toughest problems in conservation by peering into the lives of long-ago seabirds through 1,700 years of droppings.
"It's actually not so bad," said Queen's University biologist Matthew Duda, a co-author of a paper on how bird droppings found in centuries worth of lake sediments have been used to track population changes.
"It doesn't smell, very much."
The paper — a population analysis of a storm petrel colony on a remote island off Newfoundland — may seem of interest mostly to specialists. But its success in estimating the size of that population long before anyone was around to count it may have opened a whole new scientific window.
"This is a critical issue in conservation biology," said John Smol, another Queen's scientist and co-author.
"What we need to know is long-term data. We don't have those data."
Smol's lab is a leader in the study of lake sediments, layers that he calls a "time machine" into past environments.
Scientists set up shop on Baccalieu Island, about 65 kilometres north of St. John's. The island with its five lakes is home to the world's largest storm petrel colony.
The team theorized that the droppings would wash into the lake, where they would build up along with other debris on the bottom. Smol's lab normally reads layers like a book, but this was the first time scientists were working with droppings held inside the sediments.
It worked.
They analyzed six different indicators, from microorganisms that would have fed on the guano to a particular type of cholesterol unique to birds. All six gave similar results. The team's population estimates were in line with two actual surveys done on the island.
The conclusion was clear.
"By reconstructing how much bird poop gets into the pond, we can make some estimates of how big the bird populations were," Smol said. "We can reconstruct a whole spectrum of things on how the ecosystem has changed."
The team found the population of Baccalieu's storm petrels, now considered threatened and in decline, has varied widely over the last 1,700 years. At times, long before any chance of human influence, there weren't any.
The implications for conservation biology are profound.
"What is the baseline?" Smol asked.
"The population has changed dramatically without human impacts in the past. This raises a whole lot of questions.
"Now we understand we have moving baselines. It's making the world more complicated."
The method also tracks contaminants in the environment.
"You are what you eat," said Smol.
Studying droppings shows great promise for other populations as well. The team is already using it on cormorants in Lake Ontario and a Danish team is using it in Greenland.
"If we have a large enough colony of birds and there's a pond, we can reconstruct long-term bird populations," Smol said.
And he does mean long-term. Duda is using bird-dropping cores to push the storm petrel estimates back to the ice age.
The smell?
"Not so bad," said Duda.
"Because they eat fish, (storm petrels) have a pretty pungent smell. But the young, they smell quite nice — a light, fishy smell that's actually pretty pleasant.
"They are very dainty birds."
