Birds at Herbert Hoover National Historic Site: 2022 Monitoring

Female (left) and male (right) American goldfinch. Erin Anfinson, artist-in-residence; public domain via the NPS's NPGallery.

Why birds are monitored

Birds eat pests, spread seeds, pollinate plants and feed people, and birdwatching is a multi-billion-dollar industry. They are a favorite subject of park programs. They are also good indicators of environmental change — the "canary in the coal mine" that gives an ecosystem early warning.

The habitat at Herbert Hoover National Historic Site in Iowa supports a variety of birds, including species of regional concern. About 39% of the species that breed, or may breed, in the park are declining, some at alarming rates — among them the Grasshopper Sparrow, Savannah Sparrow and Western Meadowlark.

Scientists of the National Park Service's Heartland Inventory and Monitoring Network survey the park's birds during the breeding season and record the structure and makeup of the plant communities they live in. They compare the park's bird trends with those of the region. Together this shows how healthy the bird community is, how birds respond to changes in habitat, and what the park can do to restore and keep bird habitat.

The park's bird community

Surveys began in 2005. In 18 years, the network has found 74 species at the park, seventy-one of which could breed there. The number of species found, and how they were spread across the landscape, changed little over the years.

Seven breeding species are of concern in the wider region, and should be considered when the park manages its habitat:

Hoover Creek at Herbert Hoover National Historic Site. NPS.

Habitat

The park lies in the north-central part of the Eastern Tallgrass Prairie Bird Conservation Region. This region once held the tallest and lushest grasslands of the Great Plains: beech-maple forest in the east, tall prairie in the west, and oak savanna between them. Today it is mostly farmland.

The park itself is a mix of developed areas, wetland plants in places that flood seasonally, and restored tallgrass prairie — a mix that matters for the region's species of concern. About 108 breeding bird species can be found in and around the park.

Trends in common species

Nine species were seen often enough to work out yearly numbers and trends. The Red-winged Blackbird, American Robin and Dickcissel were the most abundant and widespread.

All nine had uncertain trends in the park, so comparing them with the region was inconclusive; more surveys are needed to tell whether they are rising or falling. In the region, the Dickcissel and Northern Cardinal were increasing, while the American Goldfinch, American Robin, Common Grackle, Common Yellowthroat, Eastern Meadowlark, Mourning Dove and Red-winged Blackbird were declining.

A closer look: the dickcissel

Dickcissel. G. Yellowhawk; public domain via the NPS's NPGallery.

Dickcissels breed in the prairies and old fields of the U.S. Midwest and winter in Central America and northern South America, though they are known to wander outside that range. They migrate in flocks that can number millions. Their short, buzzy song — dick-dick-ceessa-ceessa — sounds a little like their name.

They usually nest near the ground in dense grasses and sedges, raise one or two broods a year, and lay three to six eggs at a time. Females do all the parental care while males aggressively defend their territories.

On the breeding grounds, their greatest threat is loss of habitat as prairie is turned into cropland. On the wintering grounds in Venezuela, they are treated as pests that eat ripening grain, and large numbers have been killed with pesticides.

The dickcissel is a species of regional concern, but regional surveys show it increasing — and at Herbert Hoover National Historic Site it was one of the most abundant and widespread birds.

More: the full report and the Heartland Inventory and Monitoring Network.

Sources

Based on "Bird Community Monitoring at Herbert Hoover National Historic Site in Iowa, 2022," Heartland Inventory and Monitoring Network, National Park Service; a work of the United States government in the public domain. The source heads its community section "2009–2022" but says surveys began in 2005 and covers 18 years; this page follows the text.