A recent study discovered direct evidence of a species called the American woodcock, a migratory shorebird from eastern and central North America, that engages in a rare breeding strategy known as ‘itinerant breeding,’ which means they overlap periods of migration and reproduction. Migration and reproduction are two of the most challenging events in a bird’s annual cycle, with most migratory birds typically carrying out these tasks at different times of the year. However, researchers from the University of Rhode Island found that the American woodcock is an exception to this pattern.The findings reveal a unique breeding strategy known as “itinerant breeding” in the red knot, a bird species found in eastern and central North America. This strategy involves overlapping periods of migration and reproduction. The study, led by URI Ph.D. student Colby Slezak and supported by collaborators from the East Coast, was published in the scientific journal Proceedings of the Royal Society B. Slezak expressed excitement about these results, highlighting the discovery that the different stages of a bird’s annual cycle are not as distinct as previously thought. Migration, breeding, fall migration, and winter periods may not be as clearly defined as commonly believed.The woodcock is merging two energetically expensive events into one period, which is unusual as most migratory birds have distinct periods of migration and breeding. Scott McWilliams, a professor at URI, stated that most migratory birds separate these events because doing them at the same time is too costly. This case of itinerant breeding in woodcock is exceptionally rare, and documenting exceptions like this can help us understand the rules of nature.
The American woodcock, known by several nicknames such as timberdoodle, bogsucker, night partridge, and Labrador twister, is a migratory shorebird found in eastern and central North America. However, its populations have been decreasing in the last 50 years. This species is recognized for its long, needlelike bill that enables it to extract earthworms from deep in the ground, as well as the males’ intricate mating dance and “peent” call used to attract females, Slezak explained.
While there are approximately twelve bird species around the world that are believed to be itinerant breeders, this study is the first to offer direct evidence of this uncommon strategy. “They’ve sus rnrnSlezak, from Broadalbin, New York, stated “We always suspected other species of being itinerant breeders, but this is the first time we’ve had detailed GPS-tracking data and on-the-ground verification of nests to confirm that this was happening.”
The study utilized the efforts of numerous biologists from federal, state, and non-governmental agencies across the American woodcock’s flyway, from the southern U.S. into Canada. Over 350 females were tagged with GPS transmitters between 2019 and 2022 as part of the University of Maine’s Eastern Woodcock Migration Research Cooperative.Slezak, whose dissertation research included work on the study, was responsible for organizing and analyzing the tracking data. He also worked with collaborators along the bird’s range to confirm potential nesting locations. Other URI graduate students, including Liam Corcoran, Megan Gray, and Shannon Wesson, were also involved in different aspects of the woodcock project as part of a collaborative research program with biologists from the Rhode Island Department of Environmental Management Division of Fish & Wildlife.
“I was searching for brief movement patterns during the breeding season in order to identify suspected nests,” Slezak explained. “I relied on all of these collaborators from across the t.”The URI study discovered that over 80% of the tagged females nested multiple times during migration, with some nesting up to six times. On average, the females traveled about 800 kilometers between their first and second nests during northward migration, and shorter distances between subsequent nests. In 2021-22, the URI researchers verified 26 nests from 22 females, with four of them nesting repeatedly. Additionally, the study found that the researchers were able to get buy-in from people on the East Coast, who traveled to suspected nest sites, even those that were quite far away.The research found that some American woodcock migrated northward after their initial nesting attempts, with three of them making a significant journey. According to Slezak, there have been numerous reports of male woodcock singing during migration, which has been a puzzling phenomenon due to the energy required. The new data reveals that females also nest in the south, then move northward to continue nesting, suggesting that males may have breeding opportunities along their migration routes. Despite the energy demand of migration and reproduction, American woodcock have found ways to minimize the costs, such as having shorter migration routes.In comparison to other species, woodcocks can travel longer distances and can adapt to different types of young-forest habitats. Additionally, female woodcocks are larger than males and lay eggs that are small in relation to their size.
“Many other birds may not be able to do this because they do not have the same low reproductive costs that woodcocks have evolved to have,” he explained.
Another reason why woodcocks engage in itinerant breeding could be the threat of predation. Although they utilize various habitats such as wetlands and young forests with different types of trees, they often build their nests near the edges of open fields, making them vulnerable to a range of predators.
“We“I believe that most of these migratory movements after nesting are a response to predators,” he explained. “When the birds are on the nest and their eggs are eaten by predators, the female bird takes off and continues to migrate north before attempting to nest again. What we are unsure of is whether the female bird stops nesting for the rest of the year if she has a successful nest.” Despite the constant decrease in woodcock populations and their preferred young forest habitat over the past fifty years, this study brings a ray of hope for woodcock and other traveling breeders who are dealing with the challenges of ongoing human development and climate change. “Traveling breeders may be at a disadvantage due to the widespread changes in land use,” the researcher added.Slezak explained that some species of birds may have a better chance of surviving environmental changes because they are open to breeding in a wide range of environments. As long as there are suitable habitats available, the impact of these changes may be minimized. The details of this study were published in the Journal of Ornithology by Colby R. Slezak, Erik J. Blomberg, Amber M. Roth, Liam A. Berigan, Alexander C. Fish, Rachel Darling, Sarah J. Clements, Greg Balkcom, Bobbi Carpenter, Gary Costanzo, Jeffrey Duguay, Clayton L. Graham, William Harvey, Michael Hook, Douglas L. Howell, Seth Maddox, Shawn W. Meyer, Theodore C. Nichols, J. Bruce Pollard, Christian Roy, and Joshua C. Stil.ler, Jacob N. Straub, Mathieu Tetreault, Reina Tyl, Lisa Williams, Jennifer E. Kilburn, Scott R. McWilliams. Unconventional life history in a migratory shorebird: desegregating reproduction and migration. Proceedings of the Royal Society B: Biological Sciences, 2024; 291 (2021) DOI: 10.1098/rspb.2024.0021