Pea Ridge National Military Park15 ページ中 10 ページ
Fourteen years of bird monitoring at Pea Ridge National Military Park
Surveys at Pea Ridge National Military Park in Arkansas have found 111 bird species in 14 years, and the park’s bird community has been stable over that time. The Heartland Inventory and Monitoring Network has monitored the park’s birds since 2008, using them as an early warning of environmental change: the canary in the coal mine for an ecosystem.
Why birds
Birds eat pests, disperse seeds, pollinate plants and feed people, and birdwatching is a multi-billion-dollar industry. The park’s mix of woodlands and grasslands supports breeding birds, but habitat loss to agriculture and to urban and industrial development threatens bird habitat in the region around it. Of the birds that breed in the park, 23% are in decline in the region, and Bewick’s Wren, Grasshopper Sparrow and Northern Bobwhite are declining at alarming rates. During the breeding season, network scientists survey birds and the plant communities they live in, and compare park trends with the larger region’s.
Hairy Woodpeckers live in the park year-round. NPS.
What the surveys found
Monitoring uses 97 numbered points spaced evenly across the park. Most are in woodland, the park’s main vegetation type; the rest are in grassland and grassland-shrubland.
Bird monitoring locations at Pea Ridge National Military Park. NPS.
| Group | Species |
|---|---|
| Permanent or summer residents, with the potential to breed in the park | 93 |
| Winter residents | 11 |
| Transients | 6 |
| Migrant through the area | 1 |
Of the park’s breeding birds, 44 are eastern forest species and eight are grassland species; the rest are habitat generalists, wetland species or edge species. The number of species and their distribution across the park have been stable. Nine breeding species are of conservation concern for the Central Hardwoods Bird Conservation Region, in which the park lies:
| Species | Status in the park |
|---|---|
| Bald Eagle | resident |
| Bewick’s Wren | resident |
| Red-headed Woodpecker | resident |
| Blue-winged Warbler | summer resident |
| Eastern Whip-poor-will | summer resident |
| Kentucky Warbler | summer resident |
| Prairie Warbler | summer resident |
| Wood Thrush | summer resident |
| Worm-eating Warbler | summer resident |
Habitat
The park lies in the western edge of the Ozark Highland section of the Central Hardwoods region, mostly rolling hills with broad flat ridges. Historically the land held oak-hickory forest with prairie grass in the ravines and grass savanna on the ridges. When monitoring began in 2008, woodlands outnumbered grasslands three to one, and forests have been increasing throughout the Ozark Highlands. Forest thinning and stand clearing in the park since 2008 have made the woodland-to-grassland mix more balanced, which matters because the species of concern have different microhabitat needs. Red-headed Woodpeckers prefer farmlands, open woodlands, orchards and urban or suburban forest. Kentucky Warblers and Wood Thrush prefer moist deciduous bottomlands, ravines and woodlands. The others need thick shrubby or old-field and grassland habitat.
The Central Hardwoods Bird Conservation Region is one of 67 regions identified in the North American Bird Conservation Initiative. The park is on its western edge, in northwestern Arkansas. NPS.
Trends in common birds
Enough birds were counted to measure abundance for four grassland and 11 woodland species. Overall, the park’s bird community is faring similarly to, or slightly better than, the region’s.
- Blue-gray Gnatcatcher increased in the park but is in decline in the region.
- Eastern Wood-pewee and Red-eyed Vireo increased in the park and were stable in the region.
- Tufted Titmouse increased in woodland habitat on the park; its regional trend is undetermined.
- Red-bellied Woodpecker in woodland habitat is increasing in the region and was stable in the park.
- The other 10 common species had uncertain park trends, meaning no significant increase or decrease was seen, but changes of less than 5% cannot be ruled out. Most were stable in the region; Field Sparrow and Indigo Bunting are declining there.
Barred Owl is a year-round resident at the park. NPS.
Counting what is missed
Surveys do not catch every species present, which can understate the number of species. The scientists therefore use statistical estimators that draw on species distribution and abundance patterns to estimate the true number, and track the estimated and observed totals together.
Sources
- National Park Service, Heartland Inventory and Monitoring Network, “Bird Community Monitoring at Pea Ridge National Military Park, 2021”; a woodpecker photograph whose caption and description disagree is left out, and the source’s two figures for breeding species in the area are not repeated; rewritten in hubnx's own words.