Breeding Peregrine Falcons (Falco peregrinus) disappeared from Iowa in the mid-20th Century. Peregrine falcons historically nested on cliff ledges, but have also adapted to nest on human-made structures like tall buildings and bridges. Iowa DNR began a Peregrine Falcon restoration program in 1989 with 23 birds released in Cedar Rapids followed by another 19 released in Des Moines in 1991. Between 1989 and 2003, a total of 169 birds were released in Iowa feeding into a regional restoration effort that saw 875 birds released across the Midwest. In 1999, the first pair of birds nested on their historic nesting grounds along the Mississippi River bluffs. As of 2023, most of the Peregrine Falcon nesting occurs in the eastern half of the state in three main environments: Urban, Mississippi River bluff faces, and energy plant towers.
Each year, monitoring of nest sites is accomplished by a network of volunteer and professional surveyors. The Raptor Resource Project monitors and bands a number of Peregrine nest sites in the Northeastern corner of the state. Several of the nest sites are on power plants which have restricted access so we rely on employees who not only monitor the nest sites but are often wonderful stewards for the birds. Surveyors collect data on the nest’s activity and whether the pair are successful in producing fledglings. Some opportunistic reports of nesting activity are also accepted if no formal data are available.
We improved our analysis methodologies and updated historic records in 2023, thus some historic values presented in this report may appear different than previous reports. 19 nests were monitored in 2023. One new Peregrine Falcon nest was reported this year in Allamakee County which successfully fledged 2 young. Of the 19 nests, 15 were active and 4 were inactive. Of the 15 active nests, 10 were reported as successful, 3 were reported as failed, and 2 had no outcome reported. The average number of young produced per nest with a known outcome was 1.92.
Compared to recent years, 2023 was a slightly above average year for Peregrine reproduction, with a higher percentage of successful nests (66.7%) than in 2022 (50%) and similar to the rate in 2021 (68.8%). A minimum total of 25 young fledged from the 10 successful nests, slightly higher than 2022 (21) and slightly lower than 2021 (28). There was an average of 1.92 young produced per nest in 2023 which is higher than the average young produced per nest from the previous 2 years.
In 2022, Peregrine Falcons and other birds faced a unique disease challenge, the spread of a new strain of Highly Pathogenic Avian Influenza (H5N12.3.4.4). Highly Pathogenic Avian Influenza (HPAI) predominantly effects wild waterfowl and shorebirds but can also be spread to species that eat waterfowl and shorebird prey, such a Peregrine Falcons and Eagles. In 2022, the Iowa DNR documented the loss of one nesting Peregrine to HPAI. One HPAI-related death of a Peregrine was also recorded in 2023. This bird was not a nesting individual, but impacts from HPAI may have been a factor in the number of inactive nests observed this year. Overall, Iowa’s nesting population of Peregrine Falcons appears to be stable, with birds generally returning to historic nesting sites each year, but this recovering population continues to warrant annual monitoring.
Plot of the percent of active and successful Peregrine Falcon nests (out of total nests monitored) from 2016-2023.
The percent of active and successful Peregrine Falcon nests (out of total nests monitored) from 2016-2023.
A huge thank you to all of the volunteers who are vital to tracking Peregrine nesting in Iowa. The DNR will continue to monitor Peregrine Falcon nest sites with the partnership of volunteers and others who care about falcons in Iowa. Falcon nest sites can be very challenging to monitor because of their location and the territoriality of the birds so any data received are much appreciated. Please contact the Volunteer Wildlife Monitoring Program coordinator if you are interested in helping with monitoring in the future; vwmp@dnr.iowa.gov.