04 August 2022 15:00
In the soft light that filters under the canopy of the forest, ornithologist Shelly Eshleman pauses for a moment to listen. It’s just past six o’clock on a humid July morning and she, thanks to the early dawn birds’ chorus, has distinctly identified the chirping of an oriental pipilo, the species we are looking for.
As we move through the undergrowth of the Rushton woods preserve, outside
Philadelphia, Pennsylvania, I am careful to dodge a series of “fog” nets that Eshleman and his team placed that morning. They are twelve meters long nets made of very thin threads, designed to safely catch birds. The researcher hopes to lure one of these black and orange birds into the net so that she can attach a gummy-sized device to its back.
The Motus label
This small device is an ultra-light radio micro-tag, and Eshleman is one of the few scientists experimenting with its use to map the movement of birds. The pipili (papilloma erythrophthalmus) that began to mark this summer are among the first of their kind to be traced in this way. Unlike traditional radio tracking tools, which are too heavy for thrush-sized birds such as pipili, the labels used in the Motus wildlife tracking system can weigh as much as a few raindrops.
“Motus is excellent at tagging and tracking smaller animals over larger distances,” says Stu Mackenzie of Birds Canada, Ontario, a nonprofit organization that has pioneered the use of this technology.
Motus labels use radio waves to track thousands of animals, sending signals to receiving towers up to fifteen kilometers away. The technology was first introduced in 2012 by Birds Canada, but it is only with the recent expansion of the tower network that it is beginning to revolutionize the way we track migratory species and the level of detail that can be analyzed. Today, there are more than 1,400 radio towers in 31 countries.
Before the researchers had to catch the birds whenever they wanted to record their location. Now they only catch them once
We check the networks every forty minutes for the next six hours, but that morning we find no pipilo. Eshleman shows me how applying a Motus label to a similarly sized species, the cat bird (dumetella carolinensis). Carefully removes the dark gray bird from the
tightly meshed net and slides a loop of transparent elastic cord around each paw of the bird, as if making him wear a small pair of pants. Eshleman places the tag between the bird’s wings, in the center of the back. The whole process takes about two minutes.
“It’s like a fanny pack meets a backpack,” says Eshleman.
Before the advent of these new devices, researchers had to rely on aluminum bands, which were assigned a code and which were applied to the legs to track small birds. The latter then had to be captured again each time the code applied to their leg and their current position were to be recorded. With the Motus label, the bird only needs to be caught once.
The lifespan of each device depends on how often researchers program it to send a “ping” signal to the towers on the ground. The more details the scientists request, the more frequent the pings and the faster the battery of the labels drains. Hardier species, such as pipili, can be equipped with larger Motus labels with solar panels that recharge the
device indefinitely, while the smaller version of the tags used for hummingbirds and insects has an autonomy of only a few weeks.
When the Willistown conservation trust began working with Motus devices in 2017, there were only a handful of receiving towers in the northeastern United States. Since then, this foundations and other groups, which together form the Northeast Motus collaboration, have installed more than 115 receiving stations from the
Maryland to Maine. So far these receivers have collected more than 25 million coordinates, contributing to over a billion observations of 278 different species via Motus.
Over the past fifty years in North America, human activity has caused the loss of more than a quarter of the birds
“The number of stations is increasing almost every week,” says Scott Weidensaul, who used the labels to study Acadian owls (Aegolius the Acadian) on the Rushton Reservation. “We have finally gotten to the point where we can start doing the kind of research we hoped to do seven or eight years ago when these technologies weren’t there.”
New discoveries
These micro-labels are already revealing some surprises. A federally protected shorebird species, the sandpiper (warm gray hair), was known for its fondness for coastal areas, but its path between resting places was less clear. Motus labels have shown that many birds fly northwest of Pennsylvania on their journey from the New Jersey and Delaware coasts each spring, a discovery that could help choose the location of wind farms in the area, as birds can enter. collision with structures and die.
This type of insight comes at a crucial time, given the significant threats to wild fauna and flora posed by climate change and the disappearance of natural habitats. In the United States and Canada, over the past fifty years, human activity has caused the loss of more than a quarter of the birds, for an estimated total of three billion animals. According to the latest State of the world‘s birds report, it is known or suspected that around 48 percent of the world‘s birds are in demographic decline.
“The point is to know where to focus our resources to try and reverse the declines that are occurring,” says Lisa Kiziuk, director of bird conservation at the Willistown conservation trust. “We are learning a lot of things that we hadn’t even thought of studying before”.
The researchers also used the labels to track different species of thrush, a bird species that love to touch the ground, from their wintering location in South America to the northernmost regions of Canada. A Swainson’s thrush
(catharus ustulatus) labeled in Colombia was spotted in northern Saskatchewan province, Canada, a month later.
It had traveled much faster and farther than researchers would have predicted based on existing knowledge of the species: in just 34 days, the bird traveled six thousand kilometers, averaging over 175 kilometers per day.
Micro-labels make it easier than ever to follow animals on the go, and the information collected is accessible and posted online. Kiziuk says this is one of his favorite things about Motus. When people can learn about the movements of birds in their area, they are more likely to be interested in the species in their garden. This makes them more likely to contribute to the increasingly needed wildlife conservation efforts, says Kiziuk.
“You could work your whole life telling people what you see in the field and showing the data you collect, but it wouldn’t mean anything to them,” he says. “If you show a map with a bird tracing instead, people will be impressed. It’s like a light bulb that goes on. That’s what it takes ”.
(Translation by Federico Ferrone)
This article appeared in the British weekly New Scientist.