Yellowlegs Mysteries Revealed

Audubon Americas, along with partners Selva and ICESI University, started a project to place radio tags on ten Lesser Yellowlegs back in April on their wintering grounds in Colombia. Several of the birds apparently made incredible non-stop flights from there to the U.S. based on when they were detected at the MOTUS tower receiving stations that make up the network that tracks this type of tag.

After the birds moved through the U.S. in May though, the signals disappeared. 

Why?

Because these birds breed across the remote reaches of the Boreal Forest in Canada and Alaska—a region that has an abundance of sphagnum-filled bogs, which are a favorite nesting habitat of Lesser Yellowlegs. What isn't plentiful are MOTUS towers. In fact, there are very, very few in this region. It reminds me of the EZ-Pass unit on our car that registers when we drive past certain points on the turnpike and charges us for the segments we drive. When we leave the turnpike and drive on other roads, the signal from our EZ-Pass won’t be picked up. From the turnpike monitoring system’s perspective, we disappear when we are away from the receivers that pick up the signal. 

In essence, that is what happens when those tagged yellowlegs go beyond the network of MOTUS tower receivers and into the vast Boreal Forest. They disappear!

Now, some Lesser Yellowlegs are beginning their southward journeys and are reappearing. A MOTUS tower in Michigan detected the first southbound individual of the ten birds tagged in Colombia on June 23! Four more were detected from July 12 onward. 

Rather surprisingly, three of the birds passed over the same MOTUS tower in central North Dakota—one on July 12, one on July 17, and one on July 20. That seems like a pretty remarkably consistent bird highway when you consider that three out of ten tagged Lesser Yellowlegs flew over that same spot over an eight-day period!

The individual first detected in Michigan in late June is now hanging out in wetlands just south of Philadelphia. Can you imagine going from the remote and likely very quiet Boreal Forest to the hustle and bustle of that noisy landscape?

One of the birds that passed through North Dakota on July 20 made it to coastal North Carolina by the next day—a distance of about 1,500 miles! Three of the birds were last detected in the central part of the country. 

We will be excited to watch for the hoped-for detection of the remaining five tagged yellowlegs if and when they come south from the Boreal Forest. And we have so many questions. Will more of them go through North Dakota? Will all of them fly to the Atlantic Coast or will some go down to the Gulf Coast? Will they stay very long in the U.S. or will they quickly move further south? Will they migrate through the Caribbean islands or will they pass along the coast of Mexico and Central America?

Will they go back to where they were tagged in the Cauca Valley of Colombia? Will they stay there for the winter or will they move even further south? 

It is exciting to get a peek into the great mysteries of birds like the Lesser Yellowlegs and to think more deeply about the places that we humans need to protect so that they can survive through their marathon migrations.

This is the kind of vital information that will bring on-the-ground conservation solutions to help Lesser Yellowlegs and other wetland birds and other forms of biodiversity. As the world prepares for the historic COP15 meeting of the UN Convention on Biological Diversity in Montreal in December, let us hope that the leaders of the world’s nations are also thinking about the solutions and commitments that they need to help species like Lesser Yellowlegs and to reverse the declines of birds and all biodiversity.