Volunteers monitor osprey for DNR

Osprey are a migratory raptor species that breed in Iowa. Osprey experience population declines in the mid 20th century.

The Iowa Department of Natural Resources began the Osprey restoration program in 1997, translocating young birds from Minnesota and Wisconsin to strategic locations across Iowa.

The birds were last released in 2016, and the DNR is currently monitoring their nesting activity.

There are three main areas in the state where osprey have become well established: the Iowa City to Waterloo corridor, Des Moines and vicinity and Spirit Lake and vicinity (though this area is least stable).

There are also two nesting pairs on the western border of Iowa south of Sioux City.

Monitoring of nest sites is accomplished primarily by volunteers. Volunteers are assigned to particular nests, and new nests are reported opportunistically.

Volunteers visit each nest multiple times during the breeding season and try to gather information on nest activity at the start of the nesting season. They note whether the pair is successful in fledging young toward the end of the nesting season.

Some opportunistic reports of nesting activity are accepted if no formal data are available.

Fifty osprey nests were monitored during the 2024 nesting season. Of these, 39 were active and 11 were inactive.

Seven new nests were reported this year.

Of the 39 active nests, 25 succeeded in producing at least one young that survived to fledging. Five failed to do so, and outcomes for the other nine were not reported.

In 2024, 23.1% of monitored active nests had an unknown outcome. This rate is lower than last year’s 36.4%.

Based on available data, 64.1% of monitored active nests were successful (25 nests), and a minimum total of 47 young were fledged.

This is a notable increase from last year when 48.5% of monitored active nests were successful (16 nests) and a minimum total of 26 young were fledged.

An average of 1.57 young were produced per known-outcome active nest, the third highest fledge rate since 2016.

The DNR will continue to monitor osprey nest sites with the partnership of volunteers.

An ongoing challenge is that osprey like nesting on cell phone towers. Osprey don’t generally cause damage to the towers but conflicts can arise when work must be done on a tower during the nesting season, especially since over 75% of the 2024 active Iowa nest sites were on cell towers.

We will continue to work with partners on managing this potential conflict.

Anyone interested in volunteering to monitor osprey should contact the Volunteer Wildlife Monitoring Program Coordinator at vwmp@dnr.iowa.gov.