DNR monitors osprey in Iowa

Osprey, a migratory raptor species that breeds in Iowa, experienced population declines in the mid-20th Century.

The Iowa DNR began the Osprey restoration program in 1997 and involved translocating young birds from Minnesota and Wisconsin to strategic locations across Iowa.

The last year that birds were released was 2016. Currently, the objective is to monitor 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 three nesting pairs on the western border of Iowa south of Sioux City.

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

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

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

The DNR improved its analysis methodologies and updated historic records in 2023, so some historic values presented in this report may appear different from previous reports.

There were 42 osprey nests monitored during the 2023 nesting season. Of these, 33 were active and nine were inactive. Three new nests were reported this year.

Of the 33 active nests, 16 were reported successful (at least one young survived to fledging), four failed, one was gone and 12 had no outcome reported

In 2023, 36.4% of monitored active nests had an unknown outcome. This rate is the highest over the last five years of monitoring and exceeded the 2021 rate of 27.6%.

Based on available data, 48.5% of monitored active nests were successful (16 nests) and a minimum total of 26 young were fledged, though 12 nests had unknown outcomes so more young may have been produced.

An average of 1.30 young were produced per known-outcome active nest.

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 72.7% of the 2023 active Iowa nest sites were on cell towers.

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