Monday, January 23, 2012

Birds flying faster due to climate change

Wind speeds over the Southern Ocean have been increasing over the past three decades
and those stronger winds are boosting birds in the area to faster flying speeds
(picture Paul Tixier)

From DiscoveryNews

Wind speeds over the Southern Ocean have been increasing -- and pushing birds to faster speeds

Climate change has increased wind speeds, causing many birds to travel faster.
Wandering albatrosses are benefiting from the changes now, with shorter trips, improved breeding, and weight gain.
The benefits may be temporary, because pattern shifts could prevent birds from reaching foraging areas.

Wind speeds over the Southern Ocean have been increasing over the past three decades and those stronger winds are boosting birds in the area to faster flying speeds, according to new research.

The wind speed shift is linked to climate change in the study, which was published in the latest issue of Science.
The impact, at least for now, is a boon for certain birds.
It shortens the length of their foraging trips, improves their breeding success, and is even causing birds to gain over two pounds in weight.

The scientists focused their study on the wandering albatross, a bird that spends most of its life in flight, touching down on land mostly just to find food or to breed.
The windy Crozet islands in the Southern Ocean have been home to one population of such albatrosses for ages.
The researchers believe that other birds, like petrels, have been affected by the wind changes too.

"Winds have increased overall at the world's oceans, with some areas being more affected than others, but still the increase is global," lead author Henri Weimerskirch told Discovery News.
"The advantage we have with the Crozet is that we have a long term record of the population parameters, and also the movements of the birds, which is a unique situation."

Weimerskirch, a researcher at France's Centre d'Etudes Biologiques de Chize, and his team analyzed 40 year's worth of information on the Crozet albatross population.
For decades, researchers have monitored the birds' feeding and breeding, and in 1989 they began outfitting the birds with satellite transmitters to track their travels.

The researchers found that westerly winds in the Southern Ocean have increased, on average, by 15 percent over the past few decades.
Both female and male flight speeds got a boost as a result, with females alone traveling about 311 miles per day in 1990, but about 435 miles per day as of 2010.

Easier flights for the birds have improved their breeding success, allowing them to grow larger.
As it is, this species has the largest wingspan of any living bird.
It's possible that the weight gain is an adjustment to the speedier winds, allowing the birds to experience greater wing loading while in flight.

In addition to heightened wind speeds, the westerlies in the Southern Ocean are also now gradually moving poleward.
All animals in the region, from birds to their prey, have likely been affected by the changes.

"Many albatrosses and petrels are using wind for their movements, either when they search for food during central place foraging movements, or for their migratory movements over the oceans, thus these changes should undoubtedly affect many other species," Weimerskirch said.
"They should affect the food web, by increasing current strength, turbidity and therefore production, but this aspect is not well known so far."

At present, birds appear to be benefiting from the wind shifts, which the researchers attribute to climate change.
But these positive consequences of global warming may be temporary if patterns of wind in the southern westerlies follow predicted climate change scenarios.

Weimerskirch explained that models predict wind strength will continue to increase, and that the poleward shift will continue.
By 2080, the westerly flow now centered around Crozet will be further to the south, taking away the bird's easy ride.
At present the birds are also under constant threat from longline tuna fisheries, which have indirectly killed many albatrosses and other animals.

Scott Shaffer, an assistant professor of biology at San Jose State University, studied wandering albatrosses back in the late 1990s, as part of his doctoral thesis.
Shaffer told Discovery News that he was struck by the changes documented to the birds' body weight.
"This is one of the most surprising aspects of the study and is consistent with the changes in wind patterns because wind is everything to these birds and body mass changes influence their flight performance," Shaffer said.
"To see such changes over this time period is amazing."

Links :
  • LiveScience : Albatrosses soar easier on change of winds

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