Nav: Home

Migration research reveals key to declines in rare songbirds

February 26, 2018

The annual long-distance migration of rare, tiny songbirds that reproduce in the Great Lakes region and Appalachian Mountains is no longer a mystery.

By tracking one of the smallest species ever monitored over thousands of miles using cutting-edge technology, a team of ornithologists led by scientists at The University of Toledo found that it is where golden-winged warblers spend the winter in the tropics that determines if a population is declining or stable, not factors associated with the breeding grounds thousands of miles north in the United States and Canada.

Over the course of the five-year study, the scientists found that different populations of the birds, which are about the size of a ping-pong ball and weigh less than three pennies, do not mix between their separate northern nesting grounds occupied during the spring and summer and the tropical sites where they spend the winter.

Mapped using data from 76 light level geolocators recovered from the birds, each population shows strong migratory connectivity, or geographic segregation, that confirms that populations of the birds stay together in different locations for the seasons throughout the year. This strong link between breeding and non-breeding areas means that populations may be exposed to different threats and conditions during the winter.

According to the study recently published in the Proceedings of the National Academy of Sciences, golden-winged warblers from declining populations spend winters in northern South America. Stable populations of the species spend winters in Central America.

"They're separate, and it's remarkable," said Gunnar Kramer, PhD student researcher in environmental sciences at UT. "Most species we track like this don't show strong connections between breeding sites and wintering sites."

"These golden-winged warblers that breed throughout the Great Lakes region and Appalachian Mountains are going to different areas in the winter," said Dr. Henry Streby, assistant professor in the UT Department of Environmental Sciences. "That's pivotal because those tropical areas experienced different rates of forest loss during the last 60 years. When we look at forest-loss rates, it correlates closely with golden-winged warbler population changes on breeding grounds thousands of miles away."

When it comes to saving the species that is under consideration for federal Endangered Species protection, the researchers say conservationists should switch their focus away from places where their efforts cannot benefit the species and toward restoring habitat and preventing further deforestation in northern Venezuela, "which is, unfortunately, one of the most difficult places to do conservation work in the Americas," Streby said.

"If the winter habitat keeps disappearing, the warblers that winter in northern South America won't survive and come back to the Appalachian Mountains no matter how much breeding habitat is available to them," Streby said.

Kramer and Streby tracked the birds using the geolocators attached to the birds with tiny backpacks around their legs. Figure-eight harnesses secured the geolocator backpacks, which contained a battery, a computer chip and a light sensor. The whole thing weighs less than half of a paper clip and does not inhibit flight or movement.

"The light sensor records ambient light and stores it with a time stamp on the unit every couple minutes," Kramer said. "We used differences in day length and changes in how fast dawn and dusk occur to predict daily locations of the birds throughout the year. Based on how long the day and night are and features of the transitions between day and night, you can tell with reasonable accuracy where you are on the planet."

Unlike other heavier tracking devices, geolocators do not transmit data, so the researchers had to recapture every bird marked with a geolocator and remove the device to recover data.

"Comprehensive studies like this one show the importance of understanding the complex relationships migratory species have with different environments throughout the year and demonstrate that songbirds that spend the summer in our backyards may be experiencing challenging conditions elsewhere that are causing declines," Kramer said. "These studies also provide information that can immediately be used to start improving conservation efforts, and that's really exciting."
-end-
The UT researchers collaborated with scientists from several universities and agencies, including the U.S. Geological Survey, University of Tennessee and West Virginia University.

Funding was provided by the U.S. Fish and Wildlife Service, the U.S. Geological Survey and the National Science Foundation.

University of Toledo

Related Birds Articles:

Birds become immune to influenza
An influenza infection in birds gives a good protection against other subtypes of the virus, like a natural vaccination, according to a new study.
Even non-migratory birds use a magnetic compass
Not only migratory birds use a built-in magnetic compass to navigate correctly.
When birds of a feather poop together
Algal blooms deplete oxygen in lakes, produce toxins, and end up killing aquatic life in the lake.
Birds of a feather mob together
Dive bombing a much larger bird isn't just a courageous act by often smaller bird species to keep predators at bay.
Monitoring birds by drone
Forget delivering packages or taking aerial photographs -- drones can even count small birds!
The color of birds
New research provides insight into plumage evolution.
Migrating birds speed up in spring
It turns out being the early bird really does have its advantages.
Birds on top of the world, with nowhere to go
Climate change could make much of the Arctic unsuitable for millions of migratory birds that travel north to breed each year, according to a new international study published today in Global Change Biology.
City birds again prove to be angrier than rural birds
The researchers' observations shed light on the effects of human population expansion on wildlife.
Teaching drones about the birds and the bees
Unmanned Aerial Vehicles (UAVs) of the future will be able to visually coordinate their flight and navigation just like birds and flying insects do, without needing human input, radar or even GPS satellite navigation.

Related Birds Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#530 Why Aren't We Dead Yet?
We only notice our immune systems when they aren't working properly, or when they're under attack. How does our immune system understand what bits of us are us, and what bits are invading germs and viruses? How different are human immune systems from the immune systems of other creatures? And is the immune system so often the target of sketchy medical advice? Those questions and more, this week in our conversation with author Idan Ben-Barak about his book "Why Aren't We Dead Yet?: The Survivor’s Guide to the Immune System".