Tag Archives: migratory

Using Earth’s Magnetic Field as a GPS, Migratory Birds Navigate Their Way

Posted on by
Reply

Giant reed warbler migrating between Europe and Africa

AGAMI Photo Agency / Alamy Stock

Many migratory birds use the Earth's magnetic field as a compass, and others can use information from that field to more or less determine where they are on their mental map.

Greater Reed Warbler (Acrocephalus skillupaceus) appears to calculate geographic location by drawing data from various distances and angles between the magnetic field and the shape of the Earth. The study suggests that birds use magnetic information as a kind of “GPS,” telling them not only where to go, but also their initial whereabouts, they said. richard holland At Bangor University, UK.

“When we travel, we have a map that shows us where we are and a compass that shows us which direction to go to reach our destination,” he says. “We don't expect birds to have this much precision or knowledge about the entire planet. Yet, when they travel along their normal path, or even when they travel far from that path, they , and observe how the magnetic cues change.”

Scientists have known for decades that migratory birds rely on cues from the ocean. solar, star and earth's magnetic field To decide which direction to go. But using a compass to figure out direction and knowing where a bird is in the world are markedly different, and scientists are wondering if and how birds figure out their current map location. I'm still debating whether to do it or not.

Florian Packmore Germany's Lower Saxony Wadden Sea National Park Administration suspected that birds could detect detailed aspects of magnetic fields to determine their global location. Specifically, magnetic obliquity (the change in the angle of the Earth's surface relative to magnetic field lines) and magnetic declination (the difference in orientation between the geographic and magnetic poles) are used to better understand where you are in the world. He thought he might be able to do it.

To test their theory, Packmore, Holland and colleagues captured 21 adult reed warblers in Illmitz, Austria, on their migration route from Europe to Africa. So the researchers temporarily placed the birds in an outdoor aviary, where they used a Helmholtz coil to disrupt the magnetic field. They artificially altered the inclination and declination in a way that corresponded to the location of Neftekamsk, Russia, 2,600 kilometers away. “That's way off course for them,” Packmore says.

The researchers then placed the birds in special cages to study their migratory instincts and asked two independent researchers, who were unaware of changes in the magnetic field, to record which direction the birds headed. In the changed magnetic field conditions, most birds showed a clear tendency to fly west-southwest, as if trying to return to their migratory route from Russia. In contrast, when the magnetic field was unchanged, the same birds attempted to fly south-southeast from Austria.

This suggests that the birds believed they were no longer in Austria, but Russia, based solely on magnetic inclination and declination, Packmore said.

“Of course they don't know it's Russia, but it's too far north and east from where they should be,” Holland says. “And at that point, they look at their compass system and figure out how to fly south and west.”

However, the neurological mechanisms that allow birds to sense these aspects of the Earth's magnetic field are still not fully understood.

“This is an important step in understanding how the magnetic maps of songbirds, especially the great reed warbler, work,” he says. Nikita Chernetsov The professor at the Institute of Zoology of the Russian Academy of Sciences in St. Petersburg was not involved in the study.

The study confirms that the great reed warbler relies on these magnetic fields for positioning, but that doesn't mean all birds do, he added. “Not all birds work the same.”

Packmore and Holland said the birds were released two to three weeks after the study, at which point they were able to continue their normal migration. In fact, one of the birds they studied was captured a second time a year later. This means that the researchers' work did not interfere with the birds' successful migration.

topic:

Source: www.newscientist.com

The Dangers of Deadly Cold Water Gush for Migratory Sharks

Posted on by
Reply

Bull sharks may be vulnerable to cold upwelling

Martin Prohaskatz/Shutterstock

The upwelling of cold water from the deep ocean to the surface can be deadly to marine animals, and such events are becoming more frequent due to climate change.

In March 2021, hundreds of dead seafood, squid, octopus, manta rays, and bull sharks washed up on South African beaches.

The animals were fleeing high water temperatures from a marine heatwave hitting South Africa's coastal waters.

However, during their escape, they were caught in a sudden burst of cold water from the region's Agulhas Current, causing ocean temperatures to plummet.

“These upwelling events occurring on the banks of the Agulhas River could cause temperatures to suddenly drop by about 10 degrees Celsius.” [18°F] “within 24 hours” Zoe Jacobs At the UK National Marine Centre. “This is a very intense, short-term event.”

Nicholas Lubitz Professors at Australia's James Cook University used 41 years of sea surface temperature data and 33 years of sea surface temperature data to assess cold water upwelling in two regions affected by the Agulhas Current and the Australian Current, which meanders along Australia's east coast. I studied wind records.

They conclude that stronger ocean currents and changes in wind patterns associated with climate change are increasing both the frequency and strength of cold water upwelling in both regions.

Most marine organisms that live near these currents are adapted to sudden fluctuations in water temperature and can therefore cope with these changes.

However, the study warns that migratory species such as bull sharks, which pass through these waters and are unprepared for sudden changes in temperature, are at risk.

Bull sharks struggle to survive when water temperatures drop below 19°C (66°F) for extended periods. Lubitz and colleagues used data from 41 tagged bull sharks in southern Africa and Australia to study their migration patterns.

As soon as summer ends and water temperatures begin to drop, sharks migrate to warmer tropical waters. During migration, they appear to take steps to avoid cold water upwelling by moving to warmer surface waters as they swim through upwelling zones, or by seeking refuge in estuaries and bays during migration. .

But as upwelling events increase in frequency and intensity, researchers warn that it will become increasingly difficult for bull sharks and other migratory species to avoid them.

But Jacobs, who was not involved in the study, said the effects may be limited to the two areas studied. “These two particular regions of hers are very special cases because the upwelling that occurs there is a very short and intense phenomenon,” she says. Other global upwelling systems are more permanent or seasonal, and marine species are better adapted to withstand or avoid changes in water temperature, she says.

topic:

Source: www.newscientist.com

Storks refine migratory routes through experiential learning

Posted on by
Reply

Storks in their breeding grounds in Germany

Christian Ziegler/Max Planck Institute for Animal Behavior

As storks grow older, they choose faster and more direct migration routes. This suggests that storks are learning by experience to perfect these routes.

“We were able to track these animals and get detailed information about when and where they go,” he says. Ellen Aikens at the University of Wyoming. “But we wanted to learn more about how migration is refined and developed over the lifespan of storks.”

Stork (ciconia) Breeds mainly in Europe, but flies to central or southern Africa during the winter. From 2013 to 2020, Aikens and his colleagues captured 258 young storks at five breeding sites in Germany and Austria. They attached tags to them that tracked their location before releasing them.

In total, the team was able to record 301 migration events from 40 storks, with all storks completing at least two consecutive migrations.

After analyzing the data, the researchers found that young birds tend to spend more time exploring new places and trying different trails each year.

“The reason behind this is that during early childhood they collect information to better understand their environment,” Aikens said. “Because they haven’t yet bred, they have less time pressure to move into the territory they need to breed or build nests.”

However, as the storks grew, their paths gradually became straighter and they began to fly much faster in order to reach their destination faster.

“This suggests that they are progressively upgrading their routes to shorter and more direct ones, but this comes at the cost of requiring energetically more expensive transitions. ,” Aikens said. She says this change occurred because, as storks mature, they need to compete with other storks for quality nesting sites in order to be successful in breeding.

“Storks learn the same way we learn,” Aikens says. “We should appreciate more how wise and how wonderful it is that they are able to complete these journeys successfully and do better over the years.”

topic:

Source: www.newscientist.com