Background

Wood thrushes (Hylocichla mustelina) are forest-generalist neotropical migrants that have experienced significant declines across much of their range. They breed in deciduous forests of Eastern North America, and overwinter in Central and South America. Wood thrush populations have declined by approximately 1.3% yearly with a cumulative decline of 50% from 1966 to 2019 (Sauer et. al 2019). They are included on the Yellow Watch List for birds most at risk of extinction (Panjabi et. al 2021), and are on the USFWS’ Birds of Concern list (U.S. Fish and Wildlife Service, 2021). In Illinois, breeding bird survey data (1966 –2010) suggests that wood thrushes are relatively stable in much of the state, but experiencing anywhere from a -0.9% to 3% yearly decline in the northeast, east-central, and southern parts of the state (Stanley et. al 2014). Little is known about wood thrush populations on their Central and South American wintering grounds. 

Range-Wide Motus Tracking of Wood Thrush to Inform Conservation Across the Full Annual Cycle

As of 2024, our lab has been involved in the “Range-Wide Motus Tracking of Wood Thrush to Inform Conservation Across the Full Annual Cycle” project, which is an international effort led by Sarah Kendrick (USFWS) to study the migration and survival of wood thrushes. As of 2024, ~500 motus tags have been deployed on wood thrushes throughout their breeding range (26 U.S. states, Canada), with plans to deploy more tags on their Latin American wintering grounds. The goal is to ultimately deploy ~600 tags on wood thrushes to answer questions about migratory connectivity, routes, timing, and survival across the full annual cycle. With this information, the project hopes to inform conservation and management efforts. The main questions of this project are:

1. How are individual breeding and wintering populations from across these ranges linked throughout the annual cycle? 
2. How do survival rates vary across the breeding, migration, and non-breeding periods and are there measurable differences between declining and stable populations? 
3. Do population-specific differences exist in migratory timing and routes?
4. How are population trends correlated with the above and what does this mean for conservation planning? How can we focus conservation actions along migratory routes or where wood thrush appear to need it the most?
5. What can departure dates and migration speed tell us about habitat quality, and could that inform habitat management or conservation efforts for this SGCN in future? 

Summer 2024 field season

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Mike Avara and Lauren Brunk were the state contacts in Illinois for the summer 2024 field season, and were responsible for deploying 45 motus transmitters on wood thrushes throughout the state! Breeding birds that were near enough to towers to capture departure timing were tagged. The battery on these motus tags will last over a year, enabling the Ward Lab to discover both the fall and spring migration routes of tagged birds. Mike and Lauren travelled to both ends of the state to capture wood thrushes in various habitat types (ranging from the southern Illinois ravines to the Northern Illinois upland mesic forests). Of the 45 tagged birds, 7 of them remained close enough to the nearest motus tower to collect consistent, daily activity data throughout their time on the breeding grounds. This inspired Lauren’s current graduate research project – investigating the changes in activity patterns of wood thrushes throughout their full annual cycle.  

This summer 2024 effort would not have been possible without our collaborators throughout the state. Our lab wants to give a special thank you to:

1. Mike and Joann Fricke (CLIFFTOP, a Southern Illinois nonprofit) for helping us catch and tag wood thrushes and access hard-to-reach places in the southern Illinois ravines in Illinois Ozarks, White Rock, and Salt Lick Land and Water Reserve.
2. Mike Eickman (Sand Bluff Bird Observatory) and Liz Hucker (Winnebago County Forest Preserves) for helping us catch and tag wood thrushes in Colored Sands and Sugar River Alder Forest Preserves in Northern Illinois.
3. Sarah Slayton (Ward Lab) and Julia Knauz (Ward Lab) for expertly scouting wood thrush breeding territories and helping us catch and tag wood thrushes at Chain O’ Lakes State Park in Northern Illinois.
4. Tara Beveroth (INHS), Nate Beccue (Allerton), Alex Lourash (Allerton), Dave Edlund (Ward Lab), and Haley Haradon (Ward Lab) for catching and tagging wood thrushes throughout Allerton park in Central Illinois. 

Winter 2025 field season plans

In collaboration with Dr. Roberto Sosa’s Bioacoustics and Ecology Lab (El CIIDIR Unidad Oaxaca), members from the Ward Lab of Ornithology (Mike Ward, TJ Benson, Mike Avara, Lauren Brunk, Grant Wytinski, Holly Coates) will be travelling to Oaxaca, Mexico to deploy 35 motus tags on wood thrushes. This is in continued collaboration with the Range-Wide Wood Thrush project. They will deploy tags in range of an existing motus tower as well as construct more towers to track wood thrush activity patterns. This exciting opportunity will capture the movement, behavior, and departure timing of wood thrushes on their wintering grounds using the motus system!

Summer 2025 field season plans

This upcoming summer, Lauren will be using motus and accelerometer tags to track wood thrush activity rates in their breeding and post-breeding periods. These Illinois efforts are a continuous collaboration with the Range-Wide Wood Thrush project. Using nest searching/monitoring and consistent tracking of individuals to determine current breeding status, she hopes to compare activity rates between age classes, sexes, breeding attempts, as well as different periods of the full annual cycle (breeding, post-breeding, and non-breeding/overwintering). Quantifying these phenological changes in activity rate may better inform the periods and factors of highest stress for the species and inform conservation actions. 

Works Cited

1. Panjabi, A.O., W.E. Easton, P.J. Blancher, A.E. Shaw, B.A. Andres, C.J. Beardmore, A.F. Camfield, D.W. Demarest, R. Dettmers, M.A. Gahbauer, R.H. Keller, K.V. Rosenberg, and T. Will. "Avian Conservation Assessment Database Handbook, Version 2021." Partners in Flight Technical Series No. 8.2 (2021). http://pif.birdconservancy.org/acad.handbook.pdf.
2. Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link. "The North American Breeding Bird Survey, Results and Analysis 1966–2019." Version 2.07.2019. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.
3. Stanley, Calandra Q., et al. "Connectivity of wood thrush breeding, wintering, and migration sites based on range‐wide tracking." Conservation Biology 29.1 (2015): 164-174.
4. U.S. Fish and Wildlife Service. "Birds of Conservation Concern 2021." United States Department of the Interior, U.S. Fish and Wildlife Service, Migratory Birds, Falls Church, Virginia, 2021. http://www.fws.gov/birds/management/managed-species/birdsof-conservation-concern.php.
5. Wilson, R., A. Mini, C. Riley, G. Meridez, R. Gomez, E. Peresbarbarosa. "Partners in Flight Central and South American Highlands Bird Conservation Investment Strategy." Partners in Flight, 2017.