Bird monitoring at Herbert Hoover National Historic Site, Iowa: Status report 2005?2022

Abstract

In 2005, the Heartland Inventory and Monitoring Network initiated bird surveys on Herbert Hoover National Historic Site to monitor changes in bird community composition and abundance and improve our understanding of relationships between breeding birds and their habitat and the effects of management actions on those relationships. This information helps park staff plan management objectives and assess the effectiveness of management alternatives. We evaluated park breeding bird trends in the context of trends observed within the North American Bird Conservation Initiative?s Eastern Tallgrass Prairie Bird Conservation Region where the park is located. This allows us to assess the influence of park habitat management on bird populations with an understanding of regional population trends that are outside the influence of natural resource management activities at the park. Seventy-four species of birds were recorded in 18 years (2005?2022). Seventy-one of the species are considered breeding species (permanent or summer residents). Seven of these are species of concern for the Eastern Tallgrass Prairie Bird Conservation Region. Nine species were observed in sufficient numbers to calculate annual abundances and trends with some degree of statistical confidence. The Red-winged Blackbird, American Robin and Dickcissel were the most abundant and widespread species on the park. Comparisons of regional trends (2005?2019; Sauer et al. 2020) with park population trends were inconclusive. Trends in the nine abundant species on the park were uncertain. Regionally, Dickcissel and Northern Cardinal were increasing. However, American Goldfinch, American Robin, Common Grackle, Common Yellowthroat, Eastern Meadowlark, Mourning Dove, and Red-winged Blackbird were declining regionally. Diversity, richness, and evenness in distribution of individuals across species in the park breeding bird community were unchanged over the 18 years. When sampled, habitats on the plots at Herbert Hoover National Historic Site consisted primarily of the old field/prairie type, with lesser amounts of other types present. Canopy cover averaged 2 to 13% on plots, with cover provided primarily by hard?wood trees. Basal area of hardwood trees averaged between 1 and 2 m2/ha, and canopy height averaged between 4 and 5 m. Tree species from 12 different families contrib?uted to the canopy cover and basal area of plots. Plots were primarily unvegetated at ground level, with grass litter common and bare soil exposed. Total foliar cover at ground level on consisted primarily of cool season grasses and forbs.