The osprey population in Iowa is continuing to thrive, with new data from the Department of Natural Resources (DNR) revealing positive trends in their growth. According to the 2024 osprey nesting report, the success of the birds’ restoration efforts since 1997 is now visible in a robust and flourishing population.
A Steady Rise in Osprey Nesting Success
The Iowa DNR has tracked remarkable progress with osprey nesting across the state. Last year, volunteers monitored 50 osprey nests, and the 2024 report shows that 64% of those nests successfully raised fledglings—the stage when young birds can fly on their own. This marked success reflects how far Iowa’s restoration program has come since it began in 1997.
Despite the ongoing success, there are still mysteries surrounding why some nests are more successful than others. Anna Buckardt Thomas, DNR’s Avian Ecologist, notes that overall, the state has experienced a high number of fledglings in 2024.
“We’ve seen this significant growth,” Thomas said. “The population has definitely taken hold in Iowa.”
Ospreys, often referred to as fish hawks, are a species with a unique diet solely consisting of fish. The bird, once absent from Iowa, has been gradually reintroduced into the state thanks to years of restoration efforts, which included moving young birds from neighboring states like Minnesota and Wisconsin.
Osprey Restoration Success
The restoration process itself was no small feat. It spanned nearly two decades and aimed to reverse the damage done by chemicals like DDT, which decimated osprey populations in the 20th century. By 1981, the U.S. osprey population had dwindled to only 8,000 pairs due to the widespread use of organochlorines.
After decades of work, the efforts have proven fruitful. By 2024, the state was monitoring 39 active osprey nests, primarily in areas such as Des Moines, the corridor between Waterloo and Iowa City, and around Spirit Lake. These results represent a notable achievement in bringing the osprey back from the brink of local extinction.
Cell Tower Nests Pose Challenges
While there’s much to celebrate, not all is smooth sailing for Iowa’s ospreys. A significant number—about three-fourths—of the monitored nests in 2024 were found on cell phone towers. This poses challenges, especially when maintenance schedules for these towers overlap with the birds’ breeding season. Tower maintenance during this critical time can disrupt nests, forcing ospreys to abandon their eggs or young chicks.
Cell towers are not the ideal nesting sites for ospreys, but the birds have adapted to using the structures in the absence of natural trees or large poles along the waterways. These unexpected nesting spots present both opportunities and risks to the ospreys, highlighting the need for careful monitoring and sometimes intervention from local wildlife experts.
Ospreys as Indicators of Water Quality
Ospreys’ dependency on fish makes them key indicators of the health of Iowa’s water quality and fish populations. According to Buckardt Thomas, because of their unique fish-based diet, the success of osprey populations in the state is directly linked to the health of local aquatic environments. Where osprey populations thrive, it’s a positive sign that the waters they frequent are healthy, and the fish stocks are stable.
For many years, the Spirit Lake area was considered a hot spot for osprey activity. However, in recent years, the number of active nests in the area has fluctuated. In 2024, Spirit Lake had three active nests, a rise from just one nest in 2023, but still well below the five active nests observed in 2018. This fluctuation is attributed to various factors, including water quality, the availability of fish, and the specific challenges of nesting in the region.
Monitoring Osprey Nests: The Role of Volunteers
A large part of the success of the osprey restoration effort has been the involvement of local volunteers. These volunteers visit nests several times during the breeding season, monitoring the eggs and fledglings to track their development. Their efforts ensure that each nest receives the attention it needs, whether that’s confirming the eggs are incubated properly or counting how many young birds make it to the fledgling stage.
For anyone interested in contributing to this important work, Buckardt Thomas encourages Iowans to get involved. “We have a great number of volunteers already, but more volunteers are always welcome,” she said. Those interested can reach out to the DNR’s volunteer wildlife monitoring program coordinator for more information on how to get started.
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