A singing wilderness: Songbirds of the Apostle Islands

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People have been describing bird populations in the Apostle Islands since at least the early 1940s.

The first real count of breeding birds occurred in 1977, then the National Park Service began formal monitoring in 1990. There have been slight changes in monitoring methods since that time, but the top three most abundant species have stayed fairly consistent.

The most current analyses show the national lakeshore maintains high species diversity and a greater number of increasing species than decreasing ones.

These are all good signs, but monitoring helps us keep an ear out for troubling changes in the island soundtrack. 

Presenter biography

Ted Gostomski, National Park Service, Great Lakes Inventory & Monitoring Network

Ted Gostomski coordinates songbird monitoring at nine national park units in Minnesota, Wisconsin, Indiana, and Michigan for the NPS Great Lakes Inventory and Monitoring Network. His involvement with bird surveys in the Apostle Islands began in 1996 and he continues to conduct the survey on the Mainland Trail every year.

Questions and answers

How is climate change, and the accompanying warming of Lake Superior expected to affect bird populations in the islands?

One report assessed climate change vulnerability of 46 migratory bird species that breed in the upper Midwest and Great Lakes region (UMGL), incorporating the risks posed specifically by climate change (changes in moisture and temperature) and background risk (factors unrelated to climate change such as habitat loss and small population size that may predispose a species to climate vulnerability). Among ten species for whom background risk appeared to be the main factor driving vulnerability, two are songbirds that nest in the Apostle Islands: Swainson’s Thrush and Black-throated Blue Warbler. For another 14 species, climate change appeared to be most important factor raising vulnerability; eight of those are songbirds that nest in the islands: Black-and-white Warbler, Nashville Warbler, American Redstart, Yellow Warbler, Canada Warbler, Savannah Sparrow, Indigo Bunting, and Baltimore Oriole. Will these species be affected here or on their wintering grounds? Breeding season climate change was most important for American Redstarts (moisture) and Canada Warblers (temperature). Non-breeding season climate change was most important for Black-and-white Warblers (moisture), Nashville Warblers (moisture), Yellow Warblers (moisture), Indigo Buntings (moisture), and Savannah Sparrows (moisture). Baltimore Orioles are vulnerable to both breeding and non-breeding season climate change, specifically changes in moisture (i.e., increasingly dry conditions). 

How will these things affect the bird populations in the Apostle Islands? How will the birds respond? What changes will we see? The answers are species-specific, depending on each species’ capacity to adapt to whatever changes may come. The authors of this report determined adaptive capacity by scoring each species’ migration strategy (whether and how far a species migrates), breeding habitat specialization, breeding diet specialization, breeding site fidelity, nonbreeding habitat specialization, and non-breeding diet specialization. That’s a lot to consider, but the species listed above are the ones we will watch for the answers. 
Good references:  

Marra, P.P., L.A. Culp, A.L. Scarpignato, and E.B. Cohen. 2014. Full annual cycle climate change vulnerability assessment for migratory birds of the upper Midwest and Great Lakes region. The Smithsonian Conservation Biology Institute, Migratory Bird Center, Washington, D.C. www.migratoryconnectivityproject.org/climate-change-vulnerability

Matthews, S., R. O’Connor, L.R. Iverson, and A.M. Prasad. 2004. Atlas of climate change effects in 150 bird species of the Eastern United States. Gen. Tech. Rep. NE-318. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station. https://www.fs.usda.gov/treesearch/pubs/7514.  

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.

— Ted Gostomski
Science Writer/BiologistNational Park ServiceGreat Lakes Inventory and Monitoring Network

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