Pectoral sandpipers hunt for food in the mud flats of Lake Red Rock, a flood-control reservoir about 25 miles southeast of Des Moines. Photo by Stephen Dinsmore/Iowa State University. Larger image.
AMES, Iowa – Nonstop flights direct from Iowa to Venezuela are rare, unless you happen to be a well-fed pectoral sandpiper.
Pectoral sandpipers are the most common long-distance migratory shorebirds seen in Iowa, which is a convenient stopping point between their Arctic breeding grounds and their winter home in South America. And if it finds plentiful resources to refuel, a pectoral sandpiper can make Iowa its last stop before a continuous flight of around four days covering thousands of miles, research by Iowa State University ecologists found.
“Many of them didn’t stop anywhere in between Iowa and northern South America. That was surprising to us and hadn’t been documented from here before,” said Stephen Dinsmore, professor and chair of natural resource ecology and management.
Victoria Fasbender holding a tagged pectoral sandpiper at Lake Red Rock. Photo by Stephen Dinsmore/Iowa State University. Larger image.
Dinsmore and Victoria Fasbender, graduate student in wildlife ecology, monitored water bird activity the past two summers at Lake Red Rock, about 25 miles southeast of Des Moines. Red Rock is Iowa’s largest lake, a flood-control reservoir on the Des Moines River managed by the U.S. Army Corps of Engineers.
The Army Corps supported the monitoring study to gauge the impact of a practice put in place as part of the Sustainable Rivers Program, a partnership between the Army Corps and The Nature Conservancy to tweak how dams and other water infrastructure are operated to benefit aquatic life without affecting primary flood risk management functions. For about five years, the Army Corps has been lowering Lake Red Rock slightly during the late summer – by about a foot – to expose mud flats in the reservoir delta on the lake’s western edge, an ideal habitat for migrating shorebirds such as the pectoral sandpiper.
In addition to surveying how many waterbirds – and the invertebrates they eat – were in the mud flats, Fasbender and Dinsmore caught pectoral sandpipers in fine mesh nets to measure them and attach lightweight tracking tags to their back feathers. Their aim was to track the birds’ movement within the lake area. But the batteries on the tags ended up lasting longer than expected, up to two weeks. That provided the researchers a glimpse of where pectoral sandpipers went after spending, on average, about a week at Red Rock.
Of the 29 birds tagged in 2023, at least seven of them flew straight to Columbia or Venezuela after departing Iowa, according to a report prepared for the Army Corps. The longest nonstop flight was about 3,400 miles. The ambitious itineraries were amazing to document and an encouraging sign that the reservoir dropdown is working as intended, the researchers said.
“It’s definitely cool to see Iowa is having such an effect on these long-distance migratory birds, and that what we’re doing here matters to their lives,” Fasbender said.
In 2024, high water levels earlier in the summer reduced invertebrate availability at Lake Red Rock, and the difference was noticeable in the tagged pectoral sandpipers. On average, the birds flew 250% farther in 2023. Comparing data from two seasons with such differing conditions validated how critical Lake Red Rock can be to their migration patterns, Dinsmore said.
“We think that if they can find enough resources here, they’ll usually fly nonstop all the way south,” he said.
Though details aren’t set yet, the Army Corps plans to continue the research partnership with Iowa State in coming years, said Lake Red Rock natural resource specialist Perry Thostenson, who oversees the facility’s Sustainable Rivers Program and other environmental stewardship. Future studies could examine the impact of conservation-minded management at other Army Corps reservoirs in Iowa, including Saylorville Lake and Coralville Lake.
“That little bit of pool manipulation has reaped big rewards,” he said. “It’s a great way to provide another public benefit that doesn’t cost the government any extra money.”
