by Erik Blomberg, Associate Professor and Chair, Department of Wildlife Fisheries and Conservation Biology, University of Maine
Each year around the second week of March, I make a habit of standing in my central Maine backyard around dusk, waiting and hoping to hear the peent!s and twittering sky dance of the first male woodcock of spring. For me, the return of woodcock marks the true end of the Maine winter. Eight months later, sometime in November, my dog will point the last woodcock of the year, signaling the end of fall. I suspect I’m not the only one who uses woodcock migration to mark the changing seasons, regardless of what the calendar has to say about it.
The Evolution of Tracking Woodcock Migration
Wildlife biologists have puzzled over the mysteries of woodcock migration for nearly a century. In the mid-20th century, early efforts relied on recoveries of banded woodcock reported by hunters to understand the migratory connections between northern breeding areas and southern wintering grounds. Through this work, we learned that woodcock breeding in the upper Midwest and western portion of their range in Canada generally migrate along the Mississippi River and overwinter along the Gulf of Mexico. Yet birds that breed in the northeastern U.S. and eastern Canada tend to migrate along the eastern seaboard and overwinter along the Atlantic Coast. These early observations informed the designation of two regions – the Central Management Region and Eastern Management Region – which led to woodcock being monitored and managed separately in each region.
During the latter part of the 20th century, it became more common to use radio-technology to track animal movements, including woodcock, which allowed biologists to use radio receivers to follow individuals at a distance and obtain data even if they weren’t recaptured or recovered by a hunter. With radio-tracking, we gained the ability to ask how weather and the moon affect woodcock migration because we could track when individuals departed on migratory flights. The biggest limitation with radio-tracking is its relatively short range. Typically, you have to be within a few miles to obtain a woodcock’s radio-signal. The method is well-suited to knowing when a woodcock begins migration, but it’s incredibly challenging to follow the birds for hundreds or thousands of miles as they migrate.
Now in the 21st century, satellite-based telemetry has revolutionized the study of animal movements. Researchers began using satellite tags to follow Eurasian woodcock migrating between western Europe and Siberia in the early 2000s. A research group affiliated with the United States Geological Survey Cooperative Fish and Wildlife Research Units then followed suit and pioneered the use of satellite tags on American woodcock in 2013. Over a three-year period, this group, which was supported in part by RGS & AWS, collected unprecedented data on the location and timing of woodcock migration, primarily in the Central Management Region. During a summer 2016 gathering of biologists from the eastern U.S., we saw this work presented and all agreed there would be great value in repeating the research in the Eastern Management Region.
Enter the Eastern Woodcock Migration Research Cooperative
The Eastern Woodcock Migration Research Cooperative (EWMRC) was formed in 2016 with the goal of leveraging satellite tracking technology to better understand the ecology of migration and its role in affecting woodcock populations in eastern North America. The EWMRC is a collaboration of dozens of individuals representing state and federal natural resource agencies, universities and conservation nonprofit organizations in 16 U.S. states and four Canadian provinces. The cooperative is led by our research group at the University of Maine, which includes graduate students who coordinate the logistics of catching and marking birds, and managing and analyzing the resulting data.
While we employ a multi-faceted approach to studying woodcock, our most important tool has been GPS tags, which collect very precise location data from marked woodcock, regardless of where they migrate. GPS tags provide us with the location and timestamp of a marked bird every one to three days. From this, we can infer the time, route and destination of migration – all of which is found (along with archived data, interactive maps and other information), on our project website: WoodcockMigration.org.
Between 2017 and 2023, we’ve marked over 600 woodcock with GPS tags, which have migrated throughout 32 states and seven provinces. EWMRC’s collaborative nature has been key to its success, as the time, effort and funding that went into amassing a dataset of this capacity would have been impractical, if not impossible, to accomplish single-handedly. RGS & AWS was a key catalyst for the project and contributed significant funding to purchase our first GPS tags. With these, we were able to demonstrate the feasibility of the project and obtain additional funding from state and federal agencies and the initial funding invested by RGS & AWS has been matched more than 10 to 1.
Woodcock Migration is Anything but Average
The questions we can ask about woodcock migration are numerous. How far do they travel in a single night? How high do they fly while migrating? How long is their overall migration path and how many days does it take to complete migration? Like most migratory birds, woodcock stop to rest and refuel during migration – known as a stopover. How many stopovers does an average woodcock make and how long do they stay at each one? What are the conditions that cause a woodcock to begin migration or to stay at a stopover for a certain amount of time? How does spring migration differ from fall? Do adult woodcock, with the benefit of experience, migrate more efficiently than young birds on their first migration? Do males behave differently than females? What hazards do migrant woodcock encounter and how does the quality of habitat reduce the risks they face? How is all of this relevant to woodcock management?
We’re still working to answer these questions; however, after over six years of effort, we’ve chipped away at some of them. For example, the “average” woodcock in the Eastern Management Region begins fall migration around Nov. 7 and takes about four weeks to travel just under 1,000 miles to its wintering destination, stopping five or six times along the way. Most of the stopovers last a single day while around one in five stopovers is prolonged and lasts 10 days on average. Some simple math tells us that a woodcock traveling 1,000 miles and stopping six times during fall migration must be moving about 166 miles on average during each migratory flight – and our GPS tag data confirms this. Their spring return to the breeding grounds is slower with the average migration taking 6 ½ weeks to cover the same distance and requiring nine to 10 stops. We think the slower pace of spring migration is a combination of the birds waiting for northern snow cover to melt along with less-favorable prevailing winds that make migration less efficient.
While this paints the picture of an average woodcock, in reality, woodcock migration is highly variable. The timing of departure and duration of migration are very dependent on latitude. A woodcock that summers in Virginia and overwinters along the coast of North Carolina may migrate in a single flight of a few hundred miles, completing migration in a single day and making no stopovers. In contrast, a woodcock migrating from the Gaspé Peninsula in Quebec to southern Louisiana will take much longer and will need to leave earlier and make more stops. We’ve found that some woodcock don’t migrate at all; however, this is fairly uncommon with just 3% of the woodcock we’ve followed wintering and summering in the same location. Male woodcock are more rapid migrants during both fall and spring, taking 10 days fewer to migrate than the average female in both seasons. During the fall, young woodcock consistently start migration about a week later than the adult birds leaving from the same area.
I’m often reminded of how diverse woodcock migration can be when we capture and mark birds in a single location – and they do very different things. One example was two males captured in southern Florida just outside the Everglades and about as far south as woodcock spend the winter. One male migrated north and made stopovers in South Carolina, North Carolina, New York and Maine, then eventually settled for the summer on the north coast of Prince Edward Island in Canada. The second male migrated farther west, stopping in Georgia, Tennessee, Indiana and Wisconsin, then bounced across the border between Minnesota and Ontario before settling in southern Ontario for the summer. These two males were captured two days apart and within seven miles of each other, but were separated by more than 1,300 miles by the end of their migrations. Having watched data come in from hundreds of woodcock marked in the same place, it’s relatively uncommon to see two that migrate in exactly the same way.
Incredible Feats of Migration
Occasionally, migrating woodcock do some truly remarkable things. Our current record holder for the farthest distance traveled in a single night, presumably during one continuous flight, was a male captured in western Quebec in 2019. By early November he had made his way south to near the Michigan/Indiana state line and, on the night of Nov. 7, migrated to west-central Mississippi – a distance of 630 miles. This male was in Michigan at 3 P.M. on Nov. 7 and arrived in Mississippi by 9 A.M. on Nov. 8. If the bird flew under cover of darkness (roughly 12 hours that time of year), it would have traveled at a flight speed of around 50 MPH to cover the distance, presumably with the assistance of pretty favorable tailwinds. The bird didn’t stop there. Over the next three days, it flew another 250 miles to coastal Louisiana before heading back north another 320 miles where it settled into a final wintering area in northern Mississippi by Nov. 11. All told, this bird traveled more than 1,200 miles in just four days. What’s even more impressive is the bird was a young first-year male, so all of this was accomplished during his very first migration.
We’ve also observed woodcock making long-distance crossings of open water. One prominent example belongs to a woodcock marked at Cape May, New Jersey, in December 2019. The young male was captured during migration and continued south from Cape May, eventually spending the winter just north of Raleigh, North Carolina. It began its spring migration in early March, making a couple of long stopovers in southeastern Pennsylvania and upstate New York, before crossing into Canada and spending at least three days on Cape Brenton Island. The woodcock then struck out across the mouth of the Gulf of St. Lawrence, crossing several hundred miles of open water in the process. It ended its migration on the Avalon Peninsula of Newfoundland, logging locations in a roughly one square mile area until mid-August, when the transmitter stopped sending us data.
Around 2020, the manufactures of our GPS tags added a sensor that allowed us to record altitudes along with location data. Because woodcock normally migrate at night, we began programming some of the tags to collect nocturnal locations to capture migratory flights. Because an average woodcock only makes 15 such flights each year, it took a while to collect a useful dataset. What we’ve learned is woodcock normally migrate at an altitude of around 800 feet above the ground and most of the time they are below 3,000 feet. However, we’ve recorded some flights much higher with our highest recorded altitudes at more than a mile high. Woodcock also seem to migrate at higher altitudes during spring, which may be due to less favorable prevailing winds at low altitudes as the birds move northward.
Translating Science into Management
How do we use these statistics and unique observations about woodcock migration for practical application? We’re working on a number of different approaches to use our GPS-tracking data to inform management with the first one related to the way woodcock populations are monitored. Every spring, since the late 1960s, biologists and volunteers throughout the U.S. and Canada conduct evening surveys along roadside routes to count the number of male woodcock heard singing during their evening displays. These counts are used to monitor woodcock populations, track trends in woodcock abundance and to decide whether changes should be made to woodcock hunting regulations. The data is arguably one of the most important pieces of information that influence woodcock management; however, there have been a number of long-standing concerns over the survey methods.
Male woodcock begin performing their courtship displays – or sky dances – while they’re still in wintering areas and they continue to display throughout their migration north. One assumption of the singing ground survey is that when a male is recorded singing at a certain location, the bird has reached the end of migration and is a resident there. This is important because if many birds are still migrating while being counted, the survey might misrepresent local breeding densities. Biased survey data could lead to misallocation of funding to create habitat or errors in estimating woodcock population trends. A second concern is that the area covered by the survey doesn’t fully reflect the areas in which woodcock breed. If males consistently settle outside the surveyed area, then the survey may totally misrepresent the overall woodcock population.
Using data from more than 130 male woodcock that we followed on spring migration, we assessed how the timing of male migration aligned with the 20-day window during which the surveys were conducted. Because we could follow along with males until they reached the end of their migration, we could also evaluate their final breeding destinations and whether they aligned with the spatial coverage of the singing ground survey routes. In both cases, we found that the singing ground survey matched up with woodcock migration for about 90% of birds. We published these findings in the Journal of Wildlife Management last year and, in my opinion, they affirm the continued use of this important dataset for making woodcock management decisions.
Over the next few years, we plan to continue using the EWMRC dataset to advance the science of woodcock management. Ongoing work includes developing mapping tools to prioritize habitat management, understanding how woodcock habitat relationships differ during migration and on the wintering grounds and identifying the potential hazards that woodcock face during migration like those posed by nighttime light pollution or offshore wind energy development. We’re also using other tools like genetic analyses to understand how the peculiarities of woodcock migration lead to gene flow and structure populations. I hope that the information provided by the EWMRC will affect woodcock management everywhere they roam.
