Arctic Bird Shrinking as Planet Warms
An iconic shorebird that migrates from Siberia to West Africa is sending warning signals about the impact of climate change on the planet.
Just as canaries once warned miners of the lack of oxygen, an iconic shorebird that migrates from Siberia to West Africa is sending warning signals about the impact of climate change on the planet.
In a new study published today in the journal Science, an international team details how the warming of the Arctic by climate change could be responsible for drops in the population of a sub-species of red knot bird (Calidris canutus canutus).
As the Arctic has warmed, red knots - which breed in Siberia - have grown smaller with shorter bills.
When the birds arrive at their winter feeding grounds in tropical West Africa, their bills are too short to reach the best food, resulting in higher mortality among the juvenile population, the researchers found.
They suggest the red knot's experience could hold the key to understanding declining populations worldwide of migratory shore birds.
Senior author Marcel Klaassen, at the Center for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, said the Arctic was warming more rapidly than any place on the globe.
In response, many species were adapting through a process known as "body shrinkage", Klassen said.
"We observed this in the red knot bird and found they are also starting to pay the price [of this body shrinkage] once they arrive in the tropical feeding grounds," he said.
The red knot breeds in the Taimyr Peninsula in Siberia during the Arctic summer, before flying around 9,000 kilometers to Banc d'Arguin in Mauritania, West Africa.
Using satellite data from the past 33 years, the researchers found snowmelt in the high-Arctic breeding grounds of the red knot was starting earlier, changing at a rate of about half a day each year.
Over those three decades Polish researchers on the team caught and measured 1,990 red knots as the birds stopped over in Gdansk Bay on their first migration southward.
These measurements showed the body mass and bill size of juvenile birds were smaller after Arctic summers with early snowmelts.
Klaassen said the red knot breeding season was timed so that chicks would hatch when food in the form of insects was at its most abundant. "It is a very short season where there is light for 24 hours of the day and the insect life bursts at a certain moment," he said.
The earlier onset of snowmelt meant the chicks hatched after this "peak food" period and had less food available, which then impacted on their growth. This had an effect further downstream when the juvenile birds flew to their tropical non-breeding grounds where they used their tapered bills to detect and retrieve molluscs buried in mudflats.
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An analysis of the birds' blood showed individuals with a 40-millimeter bill had access to about two-thirds of the bivalves, whereas a bird with a 30-millimeter bill was able to access only one-third.
"The short bills can't reach the good food which is the shellfish and essentially become vegetarians," he said. As a result there was a massive increase in mortality rates.
Klaassen said tagging of 2,381 red knots from 2002 to 2013 and subsequent re-sightings suggested the shorter-billed birds had a 40 per cent chance of survival. This compared with longer-billed juveniles who had an 80 per cent chance of living.
He said the finding was unexpected as it was previously believed the drop-off in bird populations was due to changes in the migratory paths linked to increased human activity and changes to the environment. "This is additional bad news," he said.
Two different sub-species of red knot also migrate from Siberia to Australia during their non-breeding season. The birds were one of 49 species recently added to the endangered list. Klaassen said in Australia there was masses of data on migratory birds already collected by "legions of volunteers."
However while counts among migratory birds in Australia were also on the decline no one had looked at whether there had been changes in their body architecture.
"This study has opened our eyes. I really hadn't expected this and am keen to learn if there are similar issues here [among migratory birds]," he said.
Klaassen said more and more of these migratory birds in Australia were being placed on the list of critically endangered animals.
"Doing these long distances they need places where there is plenty of food and safety so they can concentrate on growing fat for the journey," he said. "We need to set aside areas so we can give them a chance of coping with these changes."
In an accompanying opinion piece in Science, Professor Martin Wikelski, from Germany's University of Konstanz and Grigori Tertitski, from the Russian Academy of Sciences write that the results show global warming affects life on our planet in unanticipated ways.
"Changes in one habitat may have important ecological consequences in habitats halfway around the world," they write.
They said population-level changes were occurring in many migratory animals throughout the world and cited the loss of more than 400 million songbirds in Europe over the past 30 years.
"Human societies may soon miss many of the ecosystem services, such as pest control, provided by the masses of migratory species," they said.
There was potential for these population-wide changes to be used to forecast changing conditions on the planet, but more study was required.
"Once we understand the connectivity and interactions of individual animals, we can capitalize on the superior sensing of the environment that emerges from their collective behavior," write Professor Wikelski and Tertitski.
"We may then be able to rely on animals to forecast the conditions of life on the planet that we share with them."
This originally appeared on ABC Science Online.
Red knots used to incubate their eggs in the Arctic snow in order to optimally time the hatch date of their chicks relative to the insect food peak.
Birds in flight often arrange themselves in aerodynamically optimum positions, according to a new paper in the
that helps to explain how birds fly in such impressive formations. Lead researcher Steven Portugal and his colleagues focused their study on northern bald ibises, but many bird species also exhibit the amazing flight behavior. Portugal, a University of London Royal Veterinary College researcher, told Discovery News that birds could be using three things to achieve their flying precision: "(1) vision – watching the bird in flight to get all the information they need, (2) feathers – sensing the changes in pressure, wind etc. through their flight feathers, and (3) positive feedback – i.e. they just fly around and when it feels easier/better they stay in that position."
The researchers determined that birds try to find "good air," meaning airflows (not just wind, but even the air created by other flapping wings) that minimize their energy expenditure and help them to get where they plan to go. Conversely, birds avoid regions of "bad air" that could work against them.
Many birds fly in distinctive V-formations. Portugal said, "The intricate mechanisms involved in V formation flight indicate remarkable awareness and ability of birds to respond to the wing path of nearby flock-mates. Birds in V formation seem to have developed complex phasing strategies to cope with the dynamic wakes (turbulent air) produced by flapping wings."
Military planes sometimes fly in what is known as an "echelon formation," which mirrors nearly the exact same flight formation of many birds. This particular bird version is a variation of the "V," only with a rounded edge.
The U.S. Navy's famous flight demonstration squadron The Blue Angels often flies in a trademark "diamond formation" once popularized by fighter-bomber pilots. In it, the pilots maintain an 18-inch wing tip to canopy separation. Birds can fly even more tightly together.
The term "murmuration" refers to a flock of starlings. These birds can create dramatic patterns in the sky, such as this one over marshlands near Tønder, Denmark. Other small birds, such as sandpipers, may also create what look to be dazzling aerial ballets in the sky as they fly en masse.
Even birds flying very close to land can do so in remarkable unison. Here, a formation was photographed as the birds flew over the beach at Camperduin in the Netherlands.
The classic "V" formation has all sorts of variations. In this case, three separate -- yet united -- groups create an arrow-like effect in the sky.
Alfred Hitchcock's classic horror film "The Birds" included many scenes where numerous birds blanketed the sky. Up close, these starlings look small and harmless but, as a huge murmuration, their power becomes evident.
From the earliest planes to those in design today, aircraft have been modeled after birds. It's no wonder. Every inch of this sleek northern bald ibis, snapped while flying over Tuscany, adds to the bird's flying prowess. Its 53-inch wingspan and powerful, synchronized wing beats must have captivated people in the ancient world too, since ancient Egyptians and other early cultures featured the birds prominently in their artwork and legends.