Tracking the migration and movements of grassland songbirds from Hudson Valley, NY to South America and back
by Amy Wu
At twilight Noah Perlut and his undergraduate research assistants arrived at the farm. The crunch of their rubber field boots filled the cool air as they entered the tall grass. They carried a bevy of items–a toolbox packed with rulers, colored bands to put on birds’ legs, and thumbnail-sized satellite tags, along with mist nets and palm-sized cloth bags to hold birds. Hours before dawn they were already geared up to catch Bobolinks. This was early May.
The Bobolink research initiative launched at the Farm Hub in April. The project is a collaboration between the Farm Hub and Perlut, a professor at the University of New England who has studied Bobolinks for the past 20 years. He is also a member of the Farm Hub’s Applied Farmscape Ecology Research Collaborative, a group of researchers and scientists who focus on studying the connections between farming and ecology. The Farm Hub’s Farmscape Ecology program is keen on learning more about the local Bobolink population on the farm in order to manage the farmland for both humans and wildlife.
Perlut deployed geolocators and satellite tags to track the migration and movements of Bobolinks captured at the Farm Hub. The geolocaters allow him to track the birds’ movements around the world, identifying their location with an accuracy of 50 kilometers. The devices store the data and he has to recapture these individuals next summer in order to retrieve the tag. The satellite tags are cutting edge technology that allow tracking in real time, identifying the bird’s location with an accuracy of up to within 250 meters. He is comparing birds from the Farm Hub with birds that he tracked from Shelburne Farms in Vermont. They caught six Bobolinks–five male and one female—at the Farm Hub. They also banded three Savannah Sparrows.
The palm-sized songbirds are distinct with their flat heads, spiky tails and dramatic aerial displays. In early Fall, from the northeastern U.S. and Canada, they head to Venezuela for a month, fly over the Amazon and land in Bolivia for a month, and then disperse to Argentina and Paraguay for the remainder of winter. This migration is driven by their search for food.
The current research goals are twofold: describe and compare the movement of Bobolinks at the Farm Hub with existing data from birds that breed in Vermont and explore their movements to nearby properties/farms and with other populations of Bobolinks. Perlut hopes to provide farmers in the region with the data that can help them balance their production needs with bird’s needs. Perlut noted, “These birds nest in hayfields so their reproductive success is really linked to the timing of which those hayfields are mowed. We will try to better understand what habitats they are using on and around the Farm Hub, particularly relative to when those fields are mowed.”
In the 2022 summer, Perlut and his crew will search for the birds they banding in 2021 to better understand if birds that bred there survive and return to the Farm Hub, and if birds hatched locally return to breed on the field where they hatched (as is the case in Vermont).
The May visit was fruitful for Perlut and his team of student researchers—a windfall of six Bobolinks in a matter of hours. This was not as simple as it sounds. It took an extraordinary amount of patience to untangle a Bobolink from a net.
After rapidly retrieving them from mist net to cloth bag, the team worked in tandem to tag the birds. They took a blood sample, measured their wing span and beak length, and weighed them. Perlut banded them with three color bands and one numbered metal band. These bands allow anyone with keen binoculars to identify each bird as individuals. Finally, the crew attached a tracking device, much like wearing a backpack. Four of the birds wore satellite tags that transmit the birds position to the Argos satellite system, enabling us to follow their movements in real time. Two of the birds wore geolocators, which collect and store light level and temperature data. Perlut said he would try to retrieve these geolocators next summer to assess their migration.
How it started
Perlut, now based in southern Maine, first began researching Bobolinks as a PhD student at the University of Vermont.
“This project started as my Ph.D. work and continued well past that…I was brought on to start that project in Vermont to understand the relationship between mowing and grazing relative to the birds’ (Bobolinks) reproductive success, and then the project has gone way beyond that goal mostly because of advances in tracking and molecular technology,” Perlut says. His lab focuses on tracking the birds and following their local and international migration patterns to better understand the kind of habitats they are drawn to, related these movements to what they experience on the breeding grounds. Over the course of his career, he has captured more than 4,000 Bobolinks.
Ultimately the goal is to bring knowledge to farmers and landowners so they can balance production and management goals with bird needs.
“We want to see if we can find a balance that everyone gets to meet their objectives. My experience shows that farmers are more likely to adopt creative management strategies when they know more about the individual birds that they steward in their fields,” he says.
He also enjoys sharing his knowledge and passion with the next generation. For the research project at the Farm Hub the research team included two undergraduate students from the University of New England.
Since the Bobolinks were tagged in May, Perlut and his research assistants have returned to the Farm Hub to monitor the tagged birds and look for nests. During a visit they discovered four Bobolink nests and banded 14 chicks, with the goal of seeing whether the birds that hatch on the Farm Hub return next year to breed at the farm. These nests are a hallmark of sorts, as the represent early positive returns of restoring grassland to the farm.
The team also learned that among the four satellite tags deployed, three had a software bug that caused them to malfunction after a few weeks. The good news is that the fourth satellite tag is functioning and has allowed them to track a Bobolink into its migration.
“The data has been truly amazing,” Perlut says. As of mid-August, the Bobolink had traveled roughly 70 miles south from the Farm Hub to Wantage, NJ where it spent a week on various farms before flying directly to the Blackwater National Wildlife Refuge in Maryland in early-September. As of late September, it had left Cuba and was crossing the Atlantic Ocean.
“These are tiny birds—the weight of two strawberries—and it is incredibly new to be able to track the real time movements with such precision,” he says of the satellite tags.
Despite twenty plus years of studying Bobolinks, Perlut never stops marveling at them. These tiny birds fuel themselves up on a diet of seeds and insects for a long journey. The Bobolink is in conserved tidal marsh “eating and eating to get fat and to have enough fuel to go on a super long flight,” he says. “It will add about fifty percent of its body weight before it tried to fly over the open ocean.”
On September 25 the satellite tag on the Bobolink crossing the Atlantic Ocean stopped working.
In October, “The Wonder of the Bobolink” screened at the Princeton Environmental Film Festival, and it has been selected to screen at the Nature Without Borders International Film Festival