Bird Community Monitoring at Herbert Hoover National Historic Site in Iowa, 2022

Female (left) and male (right) American Goldfinch

ERIN ANFINSON

Why Do We Monitor Birds?

Birds are an important part of the world we live in. They eat pests, disperse seeds, pollinate plants, and feed us, and birdwatching is a multi-billion-dollar industry. Park interpretive programs often feature birds because of the enjoyment they provide. Birds are also great indicators of environmental change. They serve as the canary in the coal mine for an ecosystem—an early warning system for environmental change.

Habitat at Herbert Hoover National Historic Site supports a variety of bird species, including birds of regional concern. About 39% of the species that breed or may breed in the park are in decline, and some of these species are declining at alarming rates, including Grasshopper Sparrow, Savannah Sparrow, and Western Meadowlark. Scientists in the Heartland Inventory and Monitoring Network measure changes in birds and their habitat to determine the health of bird communities and park ecosystems. During the breeding season, we survey for birds at the park and gather information about the structure and composition of the park plant communities that birds live in. We compare park bird trends with bird trends in the region. Together, this information helps us determine how healthy the park bird community is and how birds respond to changes in their habitat. Knowing how birds are doing can help the park take effective steps to restore and maintain bird habitat.

Park Bird Community (2009–2022)

We started surveying for birds at Herbert Hoover National Historic Site in 2005. In 18 years of surveys, we have found 74 bird species at the park. Seventy-one of these species have the potential to breed in the park. The number of bird species found during surveys and how they were distributed across the landscape was relatively unchanged over the years. The seven breeding species of concern (see table below) in the larger region should be considered when managing habitat on the park.

Breeding Bird Species of Conservation Concern

Birds of regional concern that have the potential to breed on the park.

Common Name	Scientific Name	Code
Blue-winged Warbler	Vermivora cyanoptera	BWWA
Dickcissel	Spiza americana	DICK
Field Sparrow	Spizella pusilla	FISP
Grasshopper Sparrow	Ammodramus savannarum	GRSP
Henslow's Sparrow	Ammodramus henslowii	HESP
Northern Flicker	Colaptes auratus	NOFL
Red-headed Woodpecker	Melanerpes erythrocephalus	RHWO

Hoover Creek at Herbert Hoover National Historic Site

NPS

Bird Habitat

Herbert Hoover National Historic Site is in the north-central section of the Eastern Tallgrass Prairie Bird Conservation Region. Historically, this region included the tallest and lushest grasslands of the Great Plains. Beech-maple forests dominated the eastern sections; tall, lush prairie dominated the western sections; and they were separated by an oak savanna. Today the region is largely agricultural. Habitat at Herbert Hoover National Historic Site is a mix of developed areas, wetland vegetation in seasonally flooded areas, and restored tallgrass prairie. This mix of habitat types at the park is important for species of regional concern. About 108 breeding bird species can be found in the habitat in and around park.

Trends of Common Bird Species

Nine bird species were observed on the park in sufficient numbers to calculate annual abundances and trends. The Red-winged Blackbird, American Robin, and Dickcissel were the most abundant and widespread species on the park. A comparison of park bird trends with regional trends was inconclusive. The nine abundant species on the park had uncertain trends. More surveys will be required to understand whether these common species are increasing or decreasing on the park. In the region, Dickcissel and Northern Cardinal were increasing, and American Goldfinch, American Robin, Common Grackle, Common Yellowthroat, Eastern Meadowlark, Mourning Dove, and Red-winged Blackbird were declining.

Dickcissel

G. YELLOWHAWK

Species Highlight: Dickcissel

Dickcissels are migratory birds that breed in the prairies and old fields of the midwestern U.S. and winter in Central America and northern South America, but they are known to wander into areas outside of their normal range. They gather in flocks as large as millions of birds to make their long migrations. The dickcissel song is a short and buzzy sounding dick-dick-ceessa-ceessa that sounds a little like it’s name. They usually build their nests near the ground in dense patches of grasses and sedges. They have one to two broods each year and lay three to six eggs at a time. Females provide all the parental care while the males are aggressively defending their territories.

The greatest threat to dickcissels on their breeding grounds is loss of habitat because of prairie conversion to crop fields. On their wintering grounds in Venezuela, dickcissels are viewed as pests that eat ripening grain crops and large numbers of birds have been killed with pesticides. Dickcissel is a species of regional concern in the Eastern Tallgrass Prairie Bird Conservation Region, but regional surveys show that it is increasing. Our surveys showed that it was one of the most abundant and widespread bird species at Herbert Hoover National Historic Site.

For More Information

Read the full report.
Visit the Heartland Inventory and Monitoring Network website.