Data from the 2024 osprey nesting report from the Iowa Department of Natural Resources shows the bird population is well established and continuing to grow in the state.

Last year, volunteers across the state monitored 50 osprey nests, and according to the 2024 report, saw 64% of the nests raise their young to the fledgling stage, or the age where the baby birds can fly, which the department considers a “successful nest.” 

The osprey, a bird of prey unique for its entirely fish-based diet, was restored to Iowa from 1997 until 2016, and now the populations are monitored by DNR. 

DNR Avian Ecologist Anna Buckardt Thomas said it is not always clear why some nests are successful and others are not, but she said Iowa had a high number of fledglings this year because of the overall growth in its osprey population. 

“The population has taken hold in Iowa,” Buckardt Thomas said.

The bird was never observed by European settlers in Iowa but tribal nations who lived in the region have accounts of the birds nesting along Iowa’s many waterways. According to DNR, osprey populations across the country were heavily affected by organochlorines, like DDT, and by 1981 the continental U.S. had just 8,000 pairs of osprey. 

The restoration process, which moved young birds from Minnesota and Wisconsin into strategic areas in Iowa, was successful. In 2024, Iowa had 39 active osprey nests, mostly in the Des Moines area, in the corridor between Waterloo and Iowa City, at Spirit Lake and near Sioux City. 

Three-fourths of the observed osprey nests in 2024 were located on top of cell phone towers, which can cause problems for the birds when tower maintenance and nesting season coincide.

Ospreys are large raptors with wingspans up to 6 feet wide, light-colored underbellies and distinctive dark markings on the underside of the wings and around the eyes.

Buckardt Thomas said because the birds subsist entirely on fish, ospreys are indicative of water quality and fish populations in the state. 

According to the report, the nests near Spirit Lake have the most fluctuation. In 2024 the area had three active nests, which was up from the singular active nest in 2023, but still down from the five active nests that were observed at the lake in 2018. 

The nests are mostly monitored by volunteers who go out several times during breeding season to see if breeding is occurring, if eggs are being incubated, how many eggs hatch and finally, how many of the young reach the fledgling stage. 

Buckardt Thomas said anyone interested in volunteering to monitor osprey nests, or any Iowan who notices a nest and wonders if it is being monitored, can email DNR’s volunteer wildlife monitoring program coordinator.

“We do have a great number of volunteers … but more volunteers is always better,” Buckardt Thomas said.

DNR is also looking for volunteers to monitor bald eagle nests and is hosting a workshop for interested volunteers on Feb. 9. In 2024, community volunteers monitored 400 eagle nests across the state. Registration for the workshop ends Feb. 6 and is mandatory.