Satellite tracking of American Woodcock reveals a gradient of migration strategies

Diversity in behavior is important for migratory birds in adapting to dynamic environmental and habitat conditions and responding to global change. Migratory behavior can be described by a variety of factors that comprise migration strategies. We characterized variation in migration strategies in American Woodcock (Scolopax minor), a migratory gamebird experiencing long-term population decline, using GPS data from approximately 300 individuals tracked throughout eastern North America. We classified woodcock migratory movements using a step-length threshold, and calculated characteristics of migration related to distance, path, and stopping events. We then used principal components analysis (PCA) to ordinate variation in migration characteristics along axes that explained different fundamental aspects of migration, and tested effects of body condition, age-sex class, and starting and ending location on PCA results. The PCA did not show evidence for clustering, suggesting a lack of discrete strategies among groups of individuals; rather, woodcock migration strategies existed along continuous gradients driven most heavily by metrics associated with migration distance and duration, departure timing, and stopping behavior. Body condition did not explain variation in migration strategy during the fall or spring, but during spring adult males and young females differed in some characteristics related to migration distance and duration. Starting and ending latitude and longitude, particularly the northernmost point of migration, explained up to 61% of the variation in any one axis of migration strategy. Our results reveal gradients in migration behavior of woodcock, and this variability should increase the resilience of woodcock to future anthropogenic landscape and climate change.

Methods
This data set contains individual bird information from banding data, in addition to migration metrics calculated from GPS tracking data for American Woodcock during spring and fall migration. Code for running and exploring results of the principal components analysis is also included.

Please visit the Eastern Woodcock Migration Research Cooperative website, woodcockmigration.org for more information about our GPS data collection methods. The raw data are also archived on Movebank (“American Woodcock Migration Ecology in Eastern North America”; Study ID 3515664596).

Data from: Satellite tracking of American Woodcock reveals a gradient of migration strategies

Sarah J. Clements, Liam A. Berigan, Alexander C. Fish, Rachel L. Darling, Amber M. Roth, Greg Balkcom, Bobbi Carpenter, Gary Costanzo, Jeffrey Duguay, Kayleigh Filkins, Clayton L. Graham, William Harvey, Michael Hook, Douglas L. Howell, Seth Maddox, Scott McWilliams, Shawn W. Mayer, Theodore C. Nichols, J. Bruce Pollard, Christian Roy, David Sausville, Colby Slezak, Josh Stiller, Jacob Straub, Mathieu Tetreault, Dawn Washington, Lisa Williams, Erik J. Blomberg