GPS-outfitted birds and citizen sightings to inform a better migration model

UNIVERSITY PARK, Pa. — Birds of a feather flock together, often traveling over enormous distances that can cross international borders. This can make managing and conserving critical populations of migratory birds extremely difficult, according to scientists at Penn State leading a team working to improve the understanding of migration movement at regional, continental and global scales. The team recently received a $848,000 grant from the U.S. National Science Foundation to support their work, which focuses on integrating two tracking methods into one powerful tool called an Integrated Movement Model.

Currently, scientists rely on two main types of information to quantify how, when and why birds migrate — movement-tracking data generated by relatively few individuals fitted with global positioning (GPS) devices and data provided by groups of citizen scientists reporting sightings.

“Our model will combine individual tracking with citizen science data, using advanced statistical and ecological models to identify behavioral sub-populations — groups of animals that move in similar ways — and model migration patterns over an entire year.” said co-principal investigator Frances Buderman, assistant professor of quantitative wildlife ecology in the College of Agricultural Sciences. “It will factor in environmental and habitat conditions, and unlike some current models, an Integrated Movement Model doesn’t just treat the movement data as static observations — it can explicitly model how and why animals move.”

The Integrated Movement Model, Buderman suggested, could be a significant upgrade for movement ecology, the field focused on how and why organisms move in response to their environment. Movement is complex, varying across time and space and among individuals, she explained. One of the current pressing questions in movement ecology is how individual movements and related impacts scale up to influence entire populations, ecosystems and biodiversity.

To answer this question, Buderman said, the team aims to create a statistical framework that integrates time-indexed location data from individual birds wearing GPS devices with reports of relative abundance generated from data collected by thousands of citizen scientists over large geographic areas. Once the model is developed, the researchers will use it to study bird migration behavior, such as quantifying which subpopulations are most likely to encounter mortality risks. For example, they will be able to assess the probability that a golden eagle that winters in Utah will encounter a wind energy development site in Montana during migration.

The researchers said they first plan to apply their model to golden eagles and mallards because both species are undergoing significant range declines and have rich telemetry datasets from birds fitted with GPS devices that provide detailed information about their movements, provided by collaborators on the NSF-funded project — the U.S. Fish and Wildlife Service (USFWS) and Tennessee Tech University. That wealth of information will allow the team to highlight the full statistical and ecological potential of an Integrated Movement Model.

According to the USFWS, the golden eagle is found worldwide, although an estimated 80% of the species’ range is in the contiguous United States. Across the country, populations of golden eagle have experienced a range-wide decline of 20% in the past 10 years. Through the team’s collaboration with the USFWS, the researchers will use GPS tracking data from hundreds of individual golden eagles.

Among waterfowl, mallards are the most harvested duck in North America, Buderman said, but in recent decades mallards have experienced a range-wide decline of 12% in the U.S. The Integrated Movement Model could help inform conservation and management of mallards, which she explained is one of the top priorities for state and federal wildlife agencies. 

Through the team’s collaboration with Bradley Cohen, assistant professor of wildlife ecology at Tennessee Tech University, the researchers have GPS tracking data on about 500 individual mallards, including males and females, adults and juveniles.

“This integrated approach will allow conservationists to make more informed, large-scale decisions based on robust data and reliable models,” Buderman said. “These models help identify critical habitats, risky migration routes, and impacts of threats like habitat loss and climate change, allowing better conservation planning for migratory species.”

Other members of the research team include Michael Shull, doctoral students in statistics at Penn State; Dave Miller, associate professor of wildlife population ecology in the Penn State College of Agricultural Sciences; Ephraim Hanks, associate professor of statistics in the Penn State Eberly College of Science; and Viviana Ruiz-Gutierrez, director of conservation science at Cornell University’s Lab of Ornithology.

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