Over the past 2,200 years, Andean condors (He is a vulture), among the world’s largest known flying birds, nest—and acacia—in a cliff cave in northern Patagonia, Argentina. Now researchers are studying the huge pile of guano to learn more about the endangered species and how it has adapted to its environment over time.
To study the doughnut-shaped mound, which is approximately 10 feet (3 meters) in diameter, the researchers carved it out like a pie, removing a 10-inch (25-centimeter) deep piece of excrement. Thanks to the site’s location inside the cave, the preserved feces were well protected from wind and rain, allowing it to accumulate over thousands of years, according to a study published May 3 in the journal Proceedings of the Royal Society B (opens in new tab).
“By looking at the different layers, we could go back in time,” lead author of the study Matthew Duda (opens in new tab), a graduate student in biology at Queen’s University in Kingston, Ontario, told Live Science. “We carbon dated [the pile] to find out the age of the nest, which is more than 2,000 years old.”
By examining the preserved droppings, the team discovered how the condor’s diet evolved over time.
“Condors are scavengers and at one time they would fly along the coasts and eat whale carcasses and native species like llamas and alpacas,” Duda said. “But as livestock such as sheep and cattle were introduced to South America [by Europeans], their diets changed along with it. We’ve seen a complete change from before to what is now most abundant to eat.”
Connected: The critically endangered condor chicks are the first known “virgin births” of the species
Unfortunately, this change also meant that the condors were ingesting more lead, which Duda attributed to “the lead shot being used to kill pests that the condors would then eat.” These toxic metals are then excreted by the birds.
“We saw that the concentration of lead is now significantly higher than in the past,” Duda said.
This is particularly worrying as Andean condors are on the Red List of Threatened Species monitored by International Union for Conservation of Nature (opens in new tab)and their numbers continue to decline, with only about 6,700 adults still living in the wild.
The researchers also noticed that over a 1,000-year period, roughly between 650 and 1650 years ago, the condors more or less abandoned the site, resulting in a drastic decrease in guano accumulation of approximately 3 cubic feet (0.08 cubic m ) per year to 0.11 cubic feet (0.003 cubic m) per year. They believe increased volcanic activity forced the condors to leave, according to the study.
“We measured an increase in sulfur and sodium, both of which are associated with volcanic activity,” said Duda, who suspects that as volcanic ash covered surrounding vegetation, herbivores were forced to leave in search of new food resources, causing the condors to take a flight too.
The researchers plan to study other Andean condor sites in the region to determine “baseline conditions” for the sites, eventually applying their methods to other threatened bird species, including oil birds (Steatornis caripensis) (opens in new tab)a nocturnal fruit-eating bird that uses echolocation to navigate.
“It is clear that quality breeding sites are critical to the survival of this species,” the study authors wrote in their paper. “To support effective conservation efforts, nesting and resting sites need extensive protection.”