The American woodcock is a favorite of bird enthusiasts and hunters alike, delighting people with its quirky walking style, bug-eyed appearance, spectacular aerial courtship displays, and (apparently) tastiness. This enigmatic species has earned several nicknames, including the evocative “bog-sucker,” “Labrador twister,” “mud bat,” and my favorite, “timberdoodle.”
Unfortunately, the woodcock has been declining throughout its range – an expanse covering much of the eastern United States and into southern Canada – since the 1960s. These birds are plump, robin-sized members of the shorebird family (Scolopacidae) that have eschewed the shore for more terrestrial habitats. However, one of the primary reasons for their decline is land-use changes and the resulting decrease in the early successional habitats that woodcock need for displaying, nesting, foraging, and roosting. Woodcock prefer open meadows and young forest and shrubland habitats (typically 2 to 20 years post-clearing). During the 1800s and first half of the 1900s, pastoral landscapes dominated the Northeast, but in the past 60 years, they have either aged out for woodcock (transitioning into mature forests) or have been developed. Additionally, logging operations that result in large tracts of regenerating vegetation have become less common in the Northeast. Early successional forest habitats now account for only about 2 percent of the landscape in the Northeast.
Other components of the woodcock’s ecology may also play a role in its decline. To better understand the challenges this species faces, biologists are asking new questions. When do birds leave the northern regions in autumn, and where do they go? When do they begin heading north in spring? What sort of habitats do they use during migration and on their wintering grounds? And what are the major risks these birds face over the annual cycle?
To answer these questions, Erik Blomberg, professor of wildlife ecology at University of Maine, created the Eastern Woodcock Migration Research Cooperative (EWMRC) in 2017. Soon thereafter, Blomberg brought on another UMaine professor, Amber Roth, to help lead the project, which now consists of more than 40 organizations from Quebec and Nova Scotia to Florida, including U.S. and Canadian government agencies, conservation organizations, hunting groups, and universities.
UMaine provides the technical assistance for the collaborative project, which entails developing protocols, curating and hosting the central database, and, when needed, showing project partners how to “tag” birds. These “tags” are GPS satellite transmitters. They weigh about 5 grams (the weight of two pennies) and are attached to the woodcock’s lower back and held in place with leg-loop bands. Each transmitter has two antennas, one to acquire a GPS location and the other to transmit the bird’s location to a satellite. Between autumn 2017 and spring 2024, EWMRC researchers deployed 737 GPS transmitters on woodcock captured in 15 states and 3 Canadian provinces.
This technology is a game-changer. Until relatively recently, tracking animal movements required researchers to put a transmitter on an animal and then to physically follow it with a large antenna, or, for a different type of tracker, to recapture the animal to collect the data from its tag. The new satellite tech “brings the data to our desk,” said Roth, “so we don’t have to go out with a truck chasing them around the continent.”
The transmitters are programmed to record and submit data at different intervals depending on the questions researchers are hoping to answer. The more frequent the data transmission rate, the shorter the battery life, so researchers must balance that tradeoff when setting the data collection schedule. Over the past 8 years, the EWMRC team has acquired a mountain of data from these transmitters (more than 40,000 locations logged). Below are a few of the group’s findings to date.
Fall migration: Not surprisingly, woodcock that spend the summer months farther north start autumn migration earlier (for example, mid-October for Ontario, Canada) than those that start autumn migration farther south (for example, mid-November for Rhode Island). Adult woodcock (>1 year old) initiate autumn migration an average of 4.1 days earlier than young birds (<1 year old). The onset of migration corresponds with the arrival of a strong tailwind, dropping air temperature, and when less of the moon is illuminated (for example, new moon versus full moon). A strong tailwind helps reduce the energetic costs of migration, whereas dropping temperatures likely signal an upcoming shortage of food as worms dig deeper to avoid frost. Less moonlight may reduce the risk of owl predation, which is a major threat to woodcock, as Roth can attest. During her master’s degree research in Wisconsin, Roth would sometimes imitate the male woodcock peent hoping a male would peent in response. “I had a couple of close calls when barred owls swooped at me,” she said. Such are the risks that come with field research.
The researchers also found that where woodcock spend the summer breeding season appears to have no relationship to where they spend winter. Woodcock wintering grounds span from southern New England to Florida in the East, and from southern Missouri to northern Mexico in the western part of their range. Birds that summer in the same breeding area might winter 1,000 miles apart from each other. For instance, two birds tagged at the same location in Vermont ended up in different wintering grounds: one in Virginia and the other in Arkansas (see map).
Spring migration: The initiation of woodcock spring migration is more closely linked to longitude than latitude, with birds farther west starting migration earlier (for example, mid-February in Louisiana) than those wintering in more eastern areas (for example, early March in Georgia and South Carolina). Males generally begin spring migration a few days before females, and the sexes appear to key in on different environmental cues for departing. Males tend to leave under low wind speed conditions and with more moon illumination, whereas females tend to leave when there is a strong tailwind and warmer air temperatures. Females therefore appear to be maximizing migratory flight efficiency and possibly timing their arrival to coincide with the reemergence of worms. Males, who are in a greater hurry to get back to claim prime displaying grounds, may have less leeway to wait for optimal flight circumstances and instead appear to take advantage of calm nighttime conditions. The pattern of leaving under greater levels of moon illumination is counter to what was observed for autumn migration, and the researchers speculate that the difference may be due to males requiring more visual assistance in navigating to suitable singing grounds at each stop northward in spring than when migrating south in autumn.
Spatial and temporal overlap of migration and breeding: One remarkable finding from the project is that woodcock are “itinerant breeders,” which means individual woodcock breed repeatedly during spring migration as they make their way north. Researchers have suspected that a handful of species worldwide use itinerant breeding, but the data from the woodcock project mark the first-time scientists have definitively documented itinerant breeding in any avian species. Researchers found that female woodcock had between one and six nesting attempts in a single season. A nesting attempt includes anything from laying a partial clutch of eggs that are immediately lost to a predator or the elements, to successfully rearing a batch of chicks to independence (which is about 5 weeks post-hatch). First breeding attempts were often south of the previously defined breeding range, occurring as far south as Florida. Many of the more southern nests often fail, said Roth, and most females then continue northward and nest again. She said nesting seems to be more successful farther north. The researchers found that females would move northward, on average, 800 kilometers (about 500 miles) between their first and second nesting attempts, and then about 200 kilometers (125 miles) between subsequent attempts.
In all other migratory birds (as far as researchers have found), breeding and migration are discrete life-history stages regulated by different hormones and physiological processes. Scientists have long considered the two stages incompatible, in part because each requires large investments of energy, which is one reason this finding is so exciting. “We used to think of these things as distinctly separate,” said Roth, and this discovery “changes the way we think about the annual cycle.”
Habitat selection during migration, breeding season, and wintering: Data on woodcock habitat use over the annual cycle indicate that the birds relax their habitat requirements during migration. That is, woodcock tolerate a greater degree of urban and industrial agriculture landcover for migratory stopover sites than for breeding or wintering sites. To help illustrate this point to her students, Roth shares an image showing the GPS points collected over eight days during migration where a bird paused at a small, wooded area in the middle of a golf course in Massachusetts. Although not a prime nesting site, it was, apparently, adequate for a mid-migration break. It may be that during migration (especially autumn migration), these birds just need a spot with some cover and some worms.
To date, the team’s findings have helped fill important gaps about the woodcock’s ecology and habitat needs over the course of the annual cycle. Land managers can use these data to make informed decisions about how to provide appropriate woodcock habitat from the breeding grounds to the wintering grounds. Similarly, wildlife officials across the woodcock’s range can use data on the woodcock’s migration ecology to ensure that hunting regulations and bag limits are data driven and appropriate for each state and province.
There is still much to be learned, and the partnerships within EWMRC are key to building on that knowledge base. “We have a great network of biologists who already know how to capture woodcock,” said Roth. “We can offer the technical support where it is needed.” These partnerships, and the collective efforts of all the members and those who care about this charismatic bird, may help turn the tide on the woodcock’s decline.