Shorebirds of the UplandsText by Joel Jorgensen
Photos by Jon Farrar
An unusual shorebird in that it spends little time on watery shorelines, the buff-breasted sandpiper has other unusual characteristics, such as the males strutting their stuff for females on display grounds. Most of the buff-breasted sandpiper population pauses each spring in the Rainwater Basin.
It’s past midnight in the middle of May and I’m in stocking feet, standing alone in a recently planted York County cornfield. There are flashes of lightning on the western horizon and in my hand I’m holding the largest fish net sold by Cabela’s. I know its six-foot metal handle is a lightening rod if the storm heads my way. I keep walking. There isn’t another person around so I’m not likely to be asked to explain what I am doing. On the Discovery Channel, great adventures in wildlife research take place in the jungles of South America, Africa and Asia, or on the tundra above the Arctic Circle. Why would a wildlife biologist choose to wander around corn and soybean fields at night in central Nebraska and consider it an adventure? The answer – to catch a buff-breasted sandpiper, a migrant shorebird that briefly stops in Nebraska each spring.
Buff-breasted sandpipers, buffies for short, are shorebirds about the size of a robin that winter in southern South America and breed in the Arctic. They are long-distance migrants, with some birds traveling more than 18,000 miles in a single year. Even though the primary migration route of buff-breasted sandpipers is through the Great Plains, they are infrequently observed, in part because, unlike most other shorebirds, they are seldom found near water. In
That buff-breasted sandpipers are shorebirds not found on shorelines is only one of their atypical characteristics. Similar to prairie-chickens and sharp-tailed grouse, the buff-breasted sandpiper is a true lekking species (leks are display grounds where groups of males display to attract females) – the only North American shorebird that has this mating system. Buffies engage in courtship displays and other social interactions during their stopover in the Rainwater Basin.
The “double-wing courtship embrace” is the male’s primary lek display, during which the male holds both wings outstretched and marches in place while tipping its bill upwards and making a barely audible tik, tik, tik sound. The undersides of a buff-breasted sandpiper’s wings are satiny white, sharply contrasting with the bird’s rich buff color. Occasionally males perform this display with no other birds in the vicinity, but usually it is initiated when another bird wanders close by. Females, sometimes two or three at a time, will stand in front of the male and be “embraced” by his outstretched wings.
The “single-wing flash” or “wing-up display” is also frequently observed during their stop in Nebraska. During this display a bird raises one wing in the air and waves it back and forth, a motion that from a distance looks like a white flag flashing in the wind. This display is most often given when other birds are flying in the vicinity, and appears to communicate where birds are congregating. Relative to most other shorebirds that have distinctive, loud calls, buffies are quiet, perhaps because their elaborate wing displays are a substitute for calls.
A Vagabond Existence
Buffies are present in significant numbers in Nebraska from about May 10 through May 23. By late-May, the number of buff-breasted sandpipers drops off rapidly as the birds continue their northward migration. Little is known of their route to the Arctic once they leave the Rainwater Basin. There are no known, key stopover sites in the Dakotas or prairie provinces
Once on their nesting grounds, males establish leks and display to attract females to mate. Males contribute nothing more than sperm to raising young. Females are tending nests in late-June. By mid-July chicks are emerging from eggs and adult males are already migrating southward. If chicks escape a host of Arctic predators, they fledge in a little less than three weeks and begin their passage south in August. By late-September and October, the buffies have returned to their wintering grounds.
During their autumn migration, buffies again pass through the Great Plains but their migration corridor is wider. Only small numbers are observed in the Rainwater Basin during their southbound migration. From both a historical and contemporary standpoint this is not surprising, as appropriate habitat is limited in late-summer. Vegetation in the Rainwater Basin landscape, whether corn or prairie, is at its peak and is too tall to be attractive. Juveniles wander even wider, with a few being found on each coast almost every fall.
A Species in Peril
The buff-breasted sandpiper is a bird of conservation concern. The species never fully recovered from unregulated sport and market hunting in the late-1800s and early-1900s, and habitat destruction and the unregulated use of highly toxic pesticides may have also contributed to their decline. Because of their status, the fact that a large proportion of the world’s buffy population stops in the Rainwater Basin during migration assigns Nebraska an important role in contributing to their conservation. Migration stopover sites that shorebirds depend on are now recognized as crucial to sustaining populations. Changes in stopover habitat, such as the loss of a particular food resource, can negatively affect populations. The Rainwater Basin has been transformed over the past two centuries from a prairie plain where herds of wild grazing animals roamed to an agricultural powerhouse producing millions of bushels of corn and soybeans each year. In order to find out how buff-breasted sandpipers are using today’s Rainwater Basin landscape, and the role their Nebraska stopover plays in the species’ annual cycle, avian biologists recognized the need to capture and track some by attaching leg bands and radio transmitters. Planning such a project is relatively easy, but carrying it out was another matter.Elusive Study Subjects
So how do you catch a small, brown bird in the middle of a cornfield in the dark of night?
In short, it’s a systematic process that involves carrying a large fishing net, walking about 50 feet, briefly turning on a spotlight to sweep the field in search of birds, then repeating the process time and time again. Having put birds to bed after sunset increases the chances of finding them later, but actually catching the birds is difficult. Many factors can cause the effort to fail – for instance, if the birds are able to recognize the human form behind the light, either by sight or sound, they flush before a net can be dropped over them. Some nights the odds are stacked against you, such as a dead calm night with a full moon – it’s difficult to sneak up on birds when you’re throwing a shadow and every step results in crackling crop stubble.
Other times conditions are favorable, but circumstances are wrong. For instance, while making a promising approach on a single buffy you might see another another bird close by but off to the side. Because it’s impossible to keep a direct light on both birds, usually one bird, both, or all birds close by flush.
All the buff-breasted sandpipers captured for this study were caught either by me or by John P. McCarty and L. LaReesa Wolfenbarger, professors at the University of Nebraska at Omaha (UNO) and co-researchers on the project. Once a buffy is caught, we carefully attach a small radio transmitter to feathers on its back. The transmitters we use for this study are small, weighing only tenths of an ounce, so they don’t impede flight or other activities. When the bird molts later in the year, the radio transmitter falls off.
We also place a metal identification band and a set of unique colored bands on each bird’s legs for identification, weigh it and measure key anatomical features such as wing length. After a bird is processed, we release it in the same field where it was captured. As many fields as possible are searched each night. If the number of birds found is encouraging, the search may go on until 3:30 in the morning. Other nights, birds may leave the fields after sundown and the search wraps up before midnight.
A night of catching birds finishes with a return to fields where a bird was radio-tagged earlier that evening. The radio receiver is turned on to check for a click, click, click as the transmitter sends its signal, indicating the bird is still in the field. The last known location of each bird is left on the voicemail of our technician, UNO student Jonas Grundman, who, at about the same time our night search ends, gathers his gear and drives to the spot where the birds were last located. His task for the next several hours is to track the position and movements of the birds with a radio receiver.What We Have Learned
The study began in 2004
The first phase of the study revealed 20,000 to 40,000 buffies paused in the Rainwater Basin. Surprisingly, those numbers were larger than the estimated size of the entire population, suggesting previous estimates were too low and that nearly all of the world’s buff-breasted sandpipers stop in the Rainwater Basin during their spring migration. We also learned that buffies are five times more likely to be found in soybean stubble than corn stubble. They also seem attracted to fields recently worked by farm implements, perhaps explaining their attraction to cornfields, as corn is being planted during their time in Nebraska.
The second-phase of our research took place from 2006 through 2008 and was again funded by UNO and a State Wildlife Grant, as well as Wildlife Conservation Fund dollars. We caught 13, 7 and 10 buffies in 2006, 2007 and 2008, respectively. While the number of birds captured is small, the information we acquired from our work has been important.
Through our measurements of captured buffies we learned they are fat when they arrive in the Rainwater Basin during spring migration. During most of the year, a male buffy weighs 1.9 to 2.3 ounces, but the average weight of the males we captured was 3.1 ounces. Stored fat is their migration fuel, so when buffies arrive in the Rainwater Basin they essentially have a full tank of gas. This tells us that birds do not need to gorge in Nebraska to continue their northward migration. As these birds make their annual migration from southern South America, they are apparently “fattening up” somewhere south of the Rainwater Basin.
Before we put our first transmitter on a bird, we assumed we would track individual birds for a few days from field to field and in the process gather information about how they used the landscape. We were surprised to find our birds did not remain in the area for any length of time: Radio-tagged birds usually left the Rainwater Basin in less than 24 hours. In 2007 and 2008, we rented an airplane to cover a larger area and locate radio signals with greater efficiency. Even then we confirmed birds were leaving after a short period of time.
Although they do not linger long in the Rainwater Basin, our research shows buff-breasted sandpipers do feed in agricultural fields. Loosely organized flocks of 20 to 50, or occasionally a few hundred, are found together. They most often feed in the morning and are least active during midday. In late-afternoon or early evening, particularly on warm days, these upland shorebirds frequent spots of standing water to drink and bathe. Migrating birds typically seek water as soon as they arrive in Nebraska. After five to 10 minutes at the water’s edge the birds seem to be refreshed and engage in courtship displays. After as little as 30 minutes the buffies usually return to fields to feed or rest.
We know buff-breasted sandpipers stop in agricultural fields in the Rainwater Basin today, but were they pausing there before European settlement transformed the landscape? While we lack any hard evidence, we are able to make some reasonable guesses. At one time, the Rainwater Basin was a nearly flat region of prairie grasses. There were more wetlands than today, and areas disturbed by native ungulates such as bison. Those heavily-grazed patches were probably suitable stopover sites. Perhaps even more important were short-cropped prairie dog colonies that would have been present. Prairie fires, albeit unpredictable, may have also provided stopover habitat for buffies and other shorebirds.
While the buffy is unique, other shorebirds also are found in agricultural fields: American golden-plovers and Baird’s sandpipers frequently are seen in the same fields. These two species have ranges and migrations similar to buff-breasted sandpipers. Historically, Eskimo curlews, now extinct, also accompanied this suite of upland shorebird species pausing in Nebraska. Early literature identifies the Rainwater Basin as an important stopover site for the curlew. Evidence suggests that the basin, a landscape defined by its shallow wetlands, was, and is, also an important stopover for birds that infrequently use wetlands.Implications
If a species’ critical habitats or food resources vanish or are altered, that species is at risk. The future of migratory shorebirds can be threatened by habitat alteration or loss at critical stopover sites. This is true even though birds pause at a site for only a few days or weeks during their annual cycle.
The Atlantic Coast population of a shorebird called the red knot is a classic example. This species has a migration and range similar to the buff-breasted sandpiper, but along the Atlantic Coast. Their key spring stopover is at Delaware Bay in New Jersey, where they feed on horseshoe crab eggs. The horseshoe crab population there has been devastated by unregulated hunting and overharvest. As a result, red knot numbers have declined precipitously and the population may become extinct within a decade. The scientific link between the decline of crabs and red knots is strong, underscoring the importance of stopover sites.
Avoiding listing a species as threatened or endangered is in the interest of everyone. Recovering species is costly and not an effective, long-term strategy to maintain wildlife populations. Comprehensive action before a species has declined to the point of needing government protection is a more cost-effective and feasible long-term strategy.
Only a few years ago, there was growing concern that buff-breasted sandpipers were edging closer to becoming listed as a threatened or endangered species. It was at that time that the question “Does anyone even know what a buff-breasted sandpiper is?” was raised at a Nebraska Game and Parks Commission meeting when funding for our initial research project was the topic. Even though it was rhetorical, it was a legitimate question – few people had ever heard of a buff-breasted sandpiper.
Our ongoing research has contributed significantly to the conservation of this species. Based on our studies, the estimate of the world’s population has been revised upward and we have documented the importance of the Rainwater Basin during the species’ 18,000-mile annual journey. While our research identified no specific threats to the species, we also do not have a complete understanding of its relationship to agriculture. The buff-breasted sandpiper is still a species of conservation concern, but our research suggests that we do not have the elements for a scenario similar to the red knot’s at Delaware Bay.
Oddly enough, most of our data about buff-breasted sandpipers came from wandering around a York County cornfield in the middle of the night in stocking feet with a spotlight and a giant fishing net.
Editor’s note: The researchers wish to acknowledge the cooperation of landowners who allowed access to their property for the study. John P. McCarty and L. LaReesa Wolfenbarger contributed to the writing of this article.