Hexbyte Glen Cove Migration routes of one of Britain's largest ducks revealed for the first time thumbnail

Hexbyte Glen Cove Migration routes of one of Britain’s largest ducks revealed for the first time

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Credit: ©Philip Croft/BTO

New research, just published in the journal Ringing & Migration, has used state of the art tracking technology to investigate how one of Britain’s largest ducks, the Shelduck, interacts with offshore wind turbines during their migration across the North Sea.

Their findings reveal—for the first time—the length, speed and flight heights of this journey.

Offshore are a key part of many governments’ strategies to reduce carbon emissions and mitigate climate change impacts. However, it is important to understand how they might affect wildlife.

The risk of colliding with , is a particular concern to travelling across the sea, and there is also a potential increased energetic cost if wind farms act as a barrier that migrating must fly around.

The majority of British and Irish Shelduck undergo a ‘moult migration’ to the Wadden Sea, which runs along the coasts of the Netherlands, Germany and Denmark. They make this journey every year in late summer, after they have finished breeding.

Once there, they replace their old and worn out feathers and become flightless in the relative safety that the Wadden Sea offers, before returning to Britain when their moult is complete. However, in journeying to and from the Wadden Sea, Shelduck must cross the North Sea and navigate its growing number of wind farms en route.

Scientists from the British Trust for Ornithology (BTO) used state of the art tags to track four Shelduck from the Alde-Ore Estuary Special Protection Area on the Suffolk coast to the Wadden Sea. Each bird took a separate route across the North Sea, and used previously unreported stopover sites in the Dutch Wadden Sea, before continuing on to moult sites in the Helgoland Bight off the coast of Germany. Incredibly, one bird travelled back and forth between the Dutch and German Wadden Seas four times, adding an extra 1,000 km to its migratory journey.

The reasons why remain a mystery.

Ros Green, Research Ecologist at BTO and lead author on the paper, said, “Having a working knowledge of species’ is an essential first step in understanding the risks that offshore wind farms may pose to populations of Shelduck and other species. Further, our tags provided data on Shelduck flight speeds and height, giving additional vital information on the magnitude of the risks posed by developments.”

She added, “It is well known that British and Irish Shelduck populations move back and forth across the North Sea each year, but this is the first published data on the specific routes taken, how long the migration takes to complete, and how fast and high Shelduck fly.”

The four Shelduck were fitted with solar powered GPS-GSM tags, allowing BTO scientists to follow their migratory movements in great detail and in almost real time, as the GPS data are downloaded over mobile phone networks.

Incredibly, although all four birds took very different routes across the North Sea, they all ended their migration in almost exactly the same place in the Dutch Wadden Sea. During the crossing, the birds flew at speeds of up to 55 knots, and up to 354 m above the sea’s surface.

The movements recorded indicated apparent interactions with several wind farm sites, though most of these are currently only at the planning phase.

Only one data fix was recorded within an operational wind farm when a bird flew within the Egmond aan Zee wind farm.

This Shelduck was flying at a height of 85 m, which would place it at potential risk of collision with the ‘s spinning turbine blades, which sweep an area between 25 and 139 m above sea level.

Indeed, the majority of the four Shelducks’ flight occurred below 150 m above sea level, which would place them in the ‘collision risk zone’ of many of the they may pass through.

The BTO team plans to extend the tracking project and collect more data to investigate whether Shelduck are actually at risk of collision, or whether the population can adapt to this essential renewable energy infrastructure.

“Further work”, the research team add, “is also needed on tagging approaches in order to extend the deployment period beyond the main moult, and capture data on the return migration. A larger sample size of tracked birds is needed before firm conclusions on Shelduck migration can be drawn. Ideally this would include birds from a wider geographical range of British breeding sites, as well as Shelduck that breed on the continent but migrate to Britain for the winter.”

More information:
Ros M.W. Green et al, Migratory movements of British and Irish Common Shelduck Tadorna tadorna: a review of ringing data and a pilot tracking study to inform potential interactions with offshore wind farms in the North Sea, Ringing & Migration (2021). DOI: 10.1080/03078698.2019.1887670

Migration routes of one of Britain’s largest ducks revealed for the first time (2021, March 16)
retrieved 16 Marc

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Hexbyte Glen Cove World migration down 30 percent due to pandemic: UN thumbnail

Hexbyte Glen Cove World migration down 30 percent due to pandemic: UN

Hexbyte Glen Cove

Credit: Pixabay/CC0 Public Domain

The coronavirus pandemic has slowed global migration by nearly 30 percent, with around two million fewer people than predicted migrating between 2019 and 2020, according to a UN report released on Friday.

Some 281 million people were living outside their country of origin in 2020.

The report, entitled “International Migration 2020,” showed that two-thirds of registered migrants lived in just 20 countries, with the United States at the top of the list, with 51 million international migrants in 2020.

Next came Germany with 16 million, Saudi Arabia with 13 million, Russia with 12 million and Britain with nine million.

India topped the list of countries with the largest diasporas in 2020, with 18 million Indians living outside their country of birth.

Other countries with a large transnational community include Mexico and Russia, each with 11 million, China with 10 million and Syria with eight million.

In 2020, the largest number of international migrants resided in Europe, with a total of 87 million.

Nearly half of international migrants resided in the region they came from, with Europe accounting for the largest share of intra-regional migration. Seventy percent of migrants born in Europe live in another European country.

Refugees account for some 12 percent of all international migrants, the report said, with around 80 percent hosted in low- and middle-income countries.

© 2021 AFP

World migration down 30 percent due to pandemic: UN (2021, January 16)
retrieved 17 January 2021
from https://phys.org/news/2021-01-world-migration-percent-due-pandemic.html


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Hexbyte Glen Cove Migration and molt affect how birds change their colors thumbnail

Hexbyte Glen Cove Migration and molt affect how birds change their colors

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Indigo buntings and other migratory birds molt before making the long trek south every fall. Credit: Eric Liffmann

In late summer and autumn, millions of birds fly above our heads, often at night, winging their way toward their wintering grounds.

Before the journey, many molt their bright feathers, replacing them with a more subdued palette. Watching this molt led scientists to wonder how color changes relate to the migrations many birds undertake twice each year. Molt matters—not only because replacing worn feathers is necessary for flight, but because molt is the catalyst for plumage changes that affect whether birds find mates and reproduce.

“We’re really blessed here, as nature lovers and birdwatchers, that we have lots of species of warblers here, which come in blues, greens, red and yellows,” said Jared Wolfe, assistant professor in Michigan Technological University’s College of Forest Resources and Environmental Science and one of the founders of the Biodiversity Initiative. “These brightly colored birds migrate and nest here and then leave for the winter. Everyone is so focused on the coloration, but the mechanism of the change of coloration is the process of molt, of replacing feathers.”

While migration distances vary, many species fly thousands of miles each year, chasing summer as the planet tilts toward and away from winter. These lengthy journeys tend to wear out feathers. In research published in the journal Ecology and Evolution, Wolfe and co-authors analyzed the variation in distances traveled against the extent of molt in a particular species. “Birds that go farther distances replace more feathers,” said Wolfe.

“Sun is the primary reason feathers degrade, and harsh environments,” he said. “In northerly latitudes in the summer, it’s sunny all day. As the birds move south, tracking the sun, they are maximally exposing themselves to sun all year.”

Feathers must be replaced because of wear and tear; what’s the significance of brightly colored plumage? Wouldn’t black be more protective against sunburn, or white better at deflecting heat?

For birds, like many animals, an attention-getting physical appearance plays a crucial role in attracting a mate. As stylish haircuts and makeup are to humans, beautiful feathers are to birds. But a spectacular plumage is also pragmatic; it broadcasts age and health, which determine who gets to mate and who doesn’t.

“Bright plumages are signals of habitat quality in the tropics,” Wolfe said. “Acquiring mates is based on a signal of habitat quality from the wintering grounds. Undergoing a second molt on the wintering grounds before migrating north allows the birds to become colorful. Color is a signal to potential mates in places like the Midwest what jungle wintering habitats are like.”

Experiences during the winter months affect how colorful birds become, which affects how successful they are at finding mates and breeding in North America. Scientists call these carryover effects. “It’s so elegant, but we’re just now starting to understand it,” Wolfe said.

Growing vibrant feathers is a physically taxing activity, and the easier a bird has it during the winter, the more brightly colored their plumage during the summer. This makes quality and , places to shelter and safety from predators important components of a wintering habitat.

Like humans seeking out coveted locations to live, birds flock to the best habitats. In both cases, resources are finite. What might have been an ideal wintering ground one year might be depleted of food sources or other important attributes the next.

“The best habitats offer resource stability over time, versus poorer quality habitats which are variable month-to-month, year-to-year,” he said.

But what about birds that don’t migrate, preferring to spend their lives within a single home range? For them, it turns out molt is comparable to changing one’s clothes on a regular basis rather than changing appearances to impress someone. Molting and breeding are constricted by multiple factors: Seasons, food abundance and size of home range play major roles in plumage and feather replacement.

“Birds here in the temperate zones are restricted in when they can breed and undergo their annual molt by winter,” Wolfe said. “In the tropics, there are wet and dry seasons, but there is less constraint from a real absence of food sources. Molt is an expensive process calorically; birds need lots and lots of food while they’re molting.”

Wolfe and his collaborators found that adjusting the time it takes Amazonian birds to complete their annual molt affects how they go about making a living. For example, ant-following birds in Brazil eat insects that are trying to outrun army ants. One tiny species, the white-plumed antbird, opportunistically darts ahead of the ants—not your garden variety ant but a species that can overpower and eat lizards, birds and small mammals in addition to insects—to take advantage of a moveable feast.

“Its molt is crazy slow; it takes an entire year,” Wolfe said, noting that the bird essentially lives in a constant state of molt, dropping one feather at a time.

Obligate antbirds have huge home ranges that overlap with multiple army ant colonies, which means they spend a large part of their day flying around the jungle in search of army ants. The bird’s lengthy daily commute is a problem when they molt wing feathers, which creates gaps in their wings and compromises their ability to fly. How do they get around this problem? A very slow molt.

“A single feather at a time to minimize gaps thereby improving their ability to fly and maintain large home ranges,” Wolfe said. “This unique adaptation has made the white-plumed antbird the slowest-molting songbird on Earth.”

Despite the predilection of migrant birds to return to the same breeding territory year after year, Wolfe and collaborators note that not all birds return to the same molting grounds. This finding confounds the assumption of home field advantage, where birds benefit from completing their annual molt in a familiar location. But it appears there isn’t much of a relationship between molting activity and what Wolfe calls “site fidelity.”

“Until our research, it had remained a mystery whether or not migratory songbirds return to the same site to molt,” Wolfe said. “This is an important question because there is growing evidence that mortalities accrued after the breeding season—during molt, migration and overwintering periods—is responsible for the continued loss of migratory songbirds. In fact, bird abundance has decreased by 29% since 1970. Understanding where and why birds molt is an important step towards protecting vulnerable populations of songbirds.”

Wolfe and colleagues used 31 years of bird banding data from northern California and southern Oregon to measure the site fidelity of 16 species of songbird during molt. While the researchers did find that breeding activity strongly correlated with site fidelity, molt did not appear to influence a bird’s decision to return to a particular place or not. It appears that birds, like humans, tend to splurge on fine feathers—and then go home to show them off.

More information:
Luiza Figueira et al, Effects of breeding and molt activity on songbird site fidelity, The Auk (2020). DOI: 10.1093/auk/ukaa053

Ryan S. Terrill et al. Evolution of breeding plumages in birds: A multiple‐step pathway to seasonal dichromatism in New World warblers (Aves: Parulidae), Ecology and Evolution (2020). DOI: 10.1002/ece3.6606


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