The roller coaster flight strategy of bar-headed geese conserves energy during Himalayan migrations

How the bar-headed geese, a 3 kg bird affront their migration across the Himalayan range?

The big question that was motivation of several documentaries was finally answered in a paper recently published in Science.

Twice a year, around 100.000 bar-headed geese migrate from Mongolia to the Indian coast. A trip of approximately 4.500 km that crosses the Himalayan range. Researchers discovered that the geese prefer to fly during the night as low as possible and without needing help from the wind. The animals do not stop beating their wings and can reach as high as 5.000 meters over sea level (flying over the 5th highest peak in the world) and descend 1.000 meters in few minutes to ascend again. The scientists compared their trip to a aerial roller coaster ride.

On average, the geese flew at an altitude of about 4500 meters, but often they changed altitude. For example, one of the four birds whose data was retrieved dropped 1000 meters in 20 minutes, then climbed more than 2000 meters in the next 1.5 hours. Yet, one bird  has been tracked migrating as high as 7290 meters, an altitude where many humans would require supplemental oxygen to move.

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Popular Pesticides Linked to Drops in Bird Populations

By Helen Thompson

Let me tell you about the birds and the bees: A family of pesticides called neonicotinoids has been linked with pollinator declines. While their involvement in bee colony collapse is hotly debated, ecologists are wondering: could neonicotinoids impact something further up the food chain?

A study published yesterday in Nature suggests that birds and bees may share a common enemy. Dutch researchers have found a correlation between bird population declines in the Netherlands and higher concentrations of the common neonicotinoid pesticide imidacloprid in surface water.

“There is an alarming trend between declines of local bird populations and imidacloprid in the environment, which needs serious attention to see what we want to do with this pesticide in the future,” says Hans de Kroon, a co-author and plant ecologist at Radboud University in the Netherlands. The researchers posit that the pesticide affects these birds by killing off their bug food supply.

Concerns have been raised about neonicotinoids’ affect on bees since the chemical first emerged on the pesticide scene in the 1990s. What makes them popular is the fact that they’re supposed to only harm insect pests keen to munch on plant leaves. In insects, the pesticide binds to specific receptors in the nervous system, ultimately killing the insect. Continue reading

Bird reproduction collapsed after oil spill

By Matt Kaplan.
Study of shag colonies on Spanish coast shows lingering effect of 2002 Prestige disaster

Jose Manuel Ribeiro/REUTERS

Volunteer workers drag fuel oil spilled by the Prestige tanker at Muxia beach, in northwestern Spain, in December 2002.

Oil spills kill a lot of wildlife quickly, but their long-term effects are hard to establish because to compare the situation before and after a disaster, a study would need to have been already up and running before the disaster occurred. Fortunately, this was precisely the case for a Spanish team of researchers.

Back in 1994, marine biologist Álvaro Barros and his colleagues at Spain’s University of Vigo started looking at the reproductive activity of 18 colonies of a diving bird known as the European shag (Phalacrocorax aristotelis). Then, on 13 November 2002, the hull of the Prestige oil tanker broke in half off the north-western coast of Spain, releasing 63,000 tonnes of oil. The oil heavily coated regions near seven of the colonies, and mostly missed the other 11, creating ‘oiled’ and ‘unoiled’ populations for the researchers to compare.

The team now reports in Biology Letters1 that reproductive success was 45% lower in oiled populations compared with unoiled colonies, whereas it had been much the same before the spill. The researchers measured reproductive success by counting how many fully grown young emerged from each nest. This number averaged 1.6 for both oiled and control colonies before the spill. Afterwards, while the control colonies maintained the 1.6 figure, the number for the birds in the oiled colonies dropped to 1.0.

“We just don’t have much information on long-term oil-spill effects. That this team was able to compare colonies like this over so many years makes the findings very valuable,” explains ecologist David Grémillet at the CNRS Centre for Functional and Evolutionary Ecology in Montpellier, France.

Barros and his team did not investigate why reproductive success was so much lower in the oiled colonies, but speculate from their knowledge of other studies that it resulted from wider ecological damage. “It looks like many of the shags’ preferred prey were wiped out, and that a lot of oil pollutants got incorporated into the ecosystem. This would certainly harm their ability to reproduce,” Barros explains.

Nature doi:10.1038/nature.2014.15130

Source: http://www.nature.com/news/bird-reproduction-collapsed-after-oil-spill-1.15130

Access to the paper: http://rsbl.royalsocietypublishing.org/content/10/4/20131041

Long-term reproductive impairment in a seabird after the Prestige oil spill

Abstract:

Large oil spills are dramatic perturbations on marine ecosystems, and seabirds are one of the worst affected organisms in such events. It has been argued that oil spills may have important long-term consequences on marine organisms, but supporting evidence remains scarce. The European shag (Phalacrocorax aristotelis) was strongly impacted at population level by the Prestige oil spill, the biggest spillage in the eastern North Atlantic. In this paper, we report on the long-term consequences on reproduction of this coastal seabird, using temporal and spatial replicated data (before–after–control–impact design). Our study revealed long-term reproductive impairment during at least the first 10 years since the Prestige oil spill. Annual reproductive success did not differ before the impact, but after the impact it was reduced by 45% in oiled colonies compared with unoiled ones. This is a rare documentation of long-term effects after a major oil spill, highlighting the need for long-term monitoring in order to assess the real impact of this type of disturbance on marine organisms.

The Secrets of Owls’ Near Noiseless Wings

Many owl species have developed specialized plumage to effectively eliminate the aerodynamic noise from their wings — allowing them to hunt and capture their prey in silence.

A research group working to solve the mystery of exactly how owls achieve this acoustic stealth will present their findings at the American Physical Society’s (APS) Division of Fluid Dynamics meeting, held Nov. 24 — 26, in Pittsburgh, Pa. — work that may one day help bring “silent owl technology” to the design of aircraft, wind turbines, and submarines.

“Owls possess no fewer than three distinct physical attributes that are thought to contribute to their silent flight capability: a comb of stiff feathers along the leading edge of the wing; a flexible fringe a the trailing edge of the wing; and a soft, downy material distributed on the top of the wing,” explained Justin Jaworski, assistant professor in Lehigh University’s Department of Mechanical Engineering and Mechanics. His group is exploring whether owl stealth is based upon a single attribute or the interaction of a combination of attributes.

For conventional wings, the sound from the hard trailing edge typically dominates the acoustic signature. But prior theoretical work carried out by Jaworski and Nigel Peake at the University of Cambridge revealed that the porous, compliant character of the owl wing’s trailing edge results in significant aerodynamic noise reductions.

“We also predicted that the dominant edge-noise source could be effectively eliminated with properly tuned porous or elastic edge properties, which implies that that the noise signature from the wing can then be dictated by otherwise minor noise mechanisms such as the ‘roughness’ of the wing surface,” said Jaworski.

The velvety down atop an owl’s wing creates a compliant but rough surface, much like a soft carpet. This down material may be the least studied of the unique owl noise attributes, but Jaworski believes it may eliminate sound at the source through a novel mechanism that is much different than those of ordinary sound absorbers.

“Our current work predicts the sound resulting from air passing over the downy material, which is idealized as a collection of individual flexible fibers, and how the aerodynamic noise level varies with fiber composition,” Jaworski said.

The researchers’ results are providing details about how a fuzzy — compliant but rough — surface can be designed to tailor its acoustic signature.

A photographic study of actual owl feathers, carried out with Ian Clark of Virginia Tech, has revealed a surprising ‘forest-like’ geometry of the down material, so this will be incorporated into the researchers’ future theoretical and experimental work to more faithfully replicate the down structure. Preliminary experiments performed at Virginia Tech show that a simple mesh covering, which replicates the top layer of the ‘forest’ structure, is effective in eliminating some sound generated by rough surfaces.

“If the noise-reduction mechanism of the owl down can be established, there may be far-reaching implications to the design of novel sound-absorbing liners, the use of flexible roughness to affect trailing-edge noise and vibrations for aircraft and wind turbines, and the mitigation of underwater noise from naval vessels,” said Jaworski.

The above story is based on materials provided by American Physical Society’s Division of Fluid Dynamics, via Newswise.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

American Physical Society’s Division of Fluid Dynamics (2013, November 24). The secrets of owls’ near noiseless wings. ScienceDaily. Retrieved November 28, 2013,

Source: http://www.sciencedaily.com­/releases/2013/11/131124093515.htm

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