Songbirds of Minong: Monitoring at Isle Royale, 2014-2018

Listening for birds along the trail between Lake Richie and the Greenstone Ridge.

NPS photo

It’s a perfect summer morning on the island—a sunrise over Lake Superior, a cool breeze to keep the mosquitoes at bay, and a symphony of birdsong. Life is grand.

The National Park Service has monitored songbird populations on Isle Royale since 1994. The variety of habitats found in the islands provide nesting areas for 89 species of songbirds. Surveys are conducted in June during the first four hours of daylight. Observers spend five minutes at each of 130 survey points distributed along eight park trails including Passage Island.

Among the four most common species at Isle Royale (left to right: Nashville Warbler, White-throated Sparrow, Winter Wren, and Ovenbird), all but the White-throated Sparrow are declining in abundance.

Photos: W.H. Majoros/Wikimedia Commons, NPS photo, NPS/W. Greene-Friends of Acadia, USFWS/S. Maslowski

2014–2018

A recent analysis of data collected from 2014 through 2018 found four species with the densest populations on the island were heard or seen most often during surveys: Nashville Warbler, White-throated Sparrow, Winter Wren, and Ovenbird. However, among those four species, all but the White-throated Sparrow showed declining trends over the five-year period. The Nashville Warbler showed the greatest decline at 6 birds/mi²/year, but this was not statistically significant. The only stastically significant trend was that of Yellow-bellied Flycatcher, declining at a rate of almost 3 birds/mi²/year.

Among guilds (a group of species that share a common trait such as habitat type, nest location, or food source), there were three increasing density trends that were not stastically significant. However, four guilds showed significant declining trends: insectivores such as warblers and flycatchers (−2 birds/mi²/year), shrub/low canopy foragers such as the thrushes (−3 birds/mi²/year), successional/scrub species such as the flicker and chickadee (−5 birds/mi²/year), and woodland species, which is most of Isle Royale’s birds (−2 birds/mi²/year).

Changing climate means a changing forest and a different bird community. Northern species (left) such as Gray Jays and Ruby-crowned Kinglets will follow the boreal forest up into Canada, while woodland and savanna species (right) such as Brown Thrashers and Wood Thrushes may expand to the island.

Photos: NPS/R.Hannawacker, NPS/K.Miller, N.Dubrow/Macaulay Library-CLO/NPS collection, USFWS/S. Maslowski.

What Will the Future Sound Like?

One study comparing bird population changes under two different climate scenarios predicted high turnover of species populations on Isle Royale by mid-century (2041–2070) if the nation continues on its current path of rising emissions¹. They offer no predictions on the future of the island’s four most common species or even the Yellow-bellied Flycatcher, but some current summer residents are expected to fare worse under future climate conditions, including the American Robin, Least Flycatcher, Mourning Warbler, and Swamp Sparrow. The Gray Jay, an iconic boreal species, is predicted to disappear from Isle Royale in the summer, while species like the Wood Thrush and the Brown Thrasher may begin to colonize the island.

It’s important to note that a changing climate is only one part of these possible changes. The habitat these birds depend on will have to shift as well. The Wood Thrush prefers a different kind of forest to the Swainson’s and Hermit Thrushes we find on the island now. And the Brown Thrasher prefers a drier, shrubbier landscape than is currently found on the island.

Change is certainly coming, but how much change remains to be seen. Birds will continue to fill the morning with song, but some of the performers may be new.

More on climate change and birds in the national parks

¹ Wu, J.X., C.B. Wilsey, L. Taylor, and G.W. Schuurman. 2018. Projected avifaunal responses to climate change across the U.S. National Park System. PLoS ONE 13(3): e0190557.
https://doi.org/10.1371/journal.pone.0190557

For more information on songbird monitoring in the Great Lakes Network parks

Great Lakes Inventory and Monitoring Network Landbird Monitoring page: www.nps.gov/im/glkn/landbirds.htm. 

Read the full report: Roberts, S.G., Z.S. Ladin, E.L. Tymkiw, W.G. Shriver, and T. Gostomski. 2021. Songbird monitoring in the Great Lakes Network parks: 2014–2018. Natural Resource Report NPS/GLKN/NRR—2021/2217. National Park Service, Fort Collins, Colorado. https://doi.org/10.36967/nrr-2283974.

Download a PDF of this article: https://irma.nps.gov/DataStore/Reference/Profile/2293414