Why Penguins Don't Fly - Pottorro kontuak

Iturria: ScienceNOW

Why Penguins Don't Fly

on 20 May 2013, 3:10 PM |  
March of the penguins. The labored flight of the
thick-billed murre (main image) helps show why 
the Emperor penguin (inset) sticks to walking and 
Credit: Kyle H. Elliott; (inset) Copyright Samuel Blanc
Long, long ago, O Best Beloved, the ancestor of the penguins could soar through the air. So why did the penguin give up flight? Rudyard Kipling never wrote a Just So story with an answer, but now scientists have one: The penguin doesn't fly because it would rather swim.
A new study of murres, penguinlike seabirds that retain the ability to take wing, shows just how costly and inefficient it is to be both a diver and a flyer. The new findings back the long-held hypothesis that penguins gave up the heavens more than 70 million years ago to become kings of the waves.
"This study contributes a lot by putting hard numbers on the energy costs of moving through both the aerial and aquatic realms," writes Daniel Ksepka of North Carolina State University in Raleigh, who studies penguin evolution and was not involved with the research, in an e-mail.
For insights into why ancestral penguins might have abandoned their command of the air, the researchers turned to the thick-billed murre, Uria lomvia, which nests on cliffs in Alaska, Canada, and other northerly sites. It propels itself through the water with its wings to scoop up krill and plankton, but it also flies—laboriously.
Murres "are awful flyers," says graduate student Kyle Elliott of the University of Manitoba in Winnipeg, Canada, an author of the new paper. "They beat their wings really, really fast, and they're horrible at landing."
To study murres nesting in northern Canada, the researchers carried shotguns loaded with rubber bullets to ward off the local polar bears and lived in a cabin surrounded by an electric "bear fence." Between surprise visits from bears, the scientists lassoed murres and injected them with tracer molecules to track their energy usage. They also outfitted the murres with sensors to learn how deep they dove and how much time they spent in air, underwater, and on land.
The results show that being a murre is hard work. The animals expend more energy per minute of flight than any other bird, surpassing even the previous champion, the bar-headed goose, famed for flying over the Himalayas. On the wing, murres burn energy at 31 times their rate at rest, the highest known ratio in a bird, the team reports today in the Proceedings of the National Academy of Sciences. When other vertebrates are working hardest, they burn energy at only 25 times their resting rate.
Murres fare better in the water, where they're more efficient than many other birds, but they could still use a few tips on their stroke. The researchers found that compared with penguins of the same size, murres expend far more energy while diving, indicating that giving up flight raised their efficiency.
The results show that murres "are really at the edge of what a bird can do," says University of Missouri, St. Louis, seabird ecologist Robert Ricklefs, an author of the paper. If the murre's all-purpose wing became more like a penguin's stubby flipper, swimming would be easier, because a short wing creates less drag in the water. But flying would be nearly impossible, because a short wing makes it harder to stay aloft.
The results run contrary to assumptions that "all birds had the same flight cost, more or less," Elliott says. For murres, "we were able to show that flight costs were much greater than expected … [and] demonstrate the cost of not being flightless." Even so, flight allows murres to flee predators and zip between nest and foraging grounds. For ancestral penguins, on the other hand, flightlessness was apparently a better deal, enabling them to grow larger, helping them dive deeper, swim faster, and stay underwater longer, Ricklefs says. And that meant they nabbed more and bigger prey.
The study provides valuable confirmation of the idea that ancient penguins swapped flight for underwater prowess, known as the tradeoff hypothesis, says Chris Thaxter, a seabird ecologist at the British Trust for Ornithology in Thetford, U.K. "This is a major step forward … in understanding how the tradeoff hypothesis works."

Seabird Bones Reveal Changes in Open-Ocean Food Chain

Iturria: ScienceDaily:

May 13, 2013 — Remains of endangered Hawaiian petrels -- both ancient and modern -- show how drastically today's open seas fish menu has changed.

Excavated bones of Hawaiian petrels – birds that spend the majority of their lives foraging the Pacific – show substantial change in the birds' eating habits. (Credit: Courtesy of Brittany Hance, Imaging Lab, Smithsonian Institution)
A research team, led by Michigan State University and Smithsonian Institution scientists, analyzed the bones of Hawaiian petrels -- birds that spend the majority of their lives foraging the open waters of the Pacific. They found that the substantial change in petrels' eating habits, eating prey that are lower rather than higher in the food chain, coincides with the growth of industrialized fishing.
The birds' dramatic shift in diet, shown in the current issue of the Proceedings of the National Academy of Sciences, leaves scientists pondering the fate of petrels as well as wondering how many other species face similar challenges.
"Our bone record is alarming because it suggests that open-ocean food webs are changing on a large scale due to human influence," said Peggy Ostrom, co-author and MSU zoologist. "Our study is among the first to address one of the great mysteries of biological oceanography -- whether fishing has gone beyond an influence on targeted species to affect nontarget species and potentially, entire food webs in the open ocean."
Hawaiian petrels' diet is recorded in the chemistry of their bones. By studying the bones' ratio of nitrogen-15 and nitrogen-14 isotopes, researchers can tell at what level in the food chain the birds are feasting; generally, the larger the isotope ratio, the bigger the prey (fish, squid and crustaceans).
Between 4,000 and 100 years ago, petrels had high isotope ratios, indicating they ate bigger prey. After the onset of industrial fishing, which began extending past the continental shelves around 1950, the isotope ratios declined, indicating a species-wide shift to a diet of smaller fish and other prey.
Much research has focused on the impact of fishing near the coasts. In contrast, the open ocean covers nearly half of Earth's surface. But due to a lack of historical records, fishing's impact on most open-ocean animal populations is completely unknown, said lead author Anne Wiley, formerly an MSU doctoral student and now a Smithsonian postdoctoral researcher.
"Hawaiian petrels spend the majority of their lives foraging over vast expanses of open ocean," she said. "In their search for food, they've done what scientists can only dream of. For thousands of years, they've captured a variety of fish, squid and crustaceans from a large portion of the North Pacific Ocean, and a record of their diet is preserved in their bones."
Addressing fishery impact through a chronology of bones is remarkable. Most marine animals die at sea, where their bones are buried on the ocean bottom. But after three decades of fossil collection in the Hawaiian Islands -- the breeding grounds of the Hawaiian petrel -- co-author Helen James of the Smithsonian Institution and her colleagues have amassed a collection of more than 17,000 ancient Hawaiian petrel bones.
"The petrels breed in burrows and caves where, if they die, their bones are likely to be preserved for a long time," James said. "It's fortuitous to find such a rich bone record for a rare oceanic predator."
Further studies are needed to explore how the shift down the food chain is affecting Hawaiian petrels. For a coastal seabird, however, a similar shift in diet has been associated with decreases in population -- bad news for a federally protected bird.
Since petrels exploit fishing grounds from the equator to near the Aleutian Islands -- an area larger than the continental United States -- their foraging habits are quite telling. If petrels, signal flares for open-ocean food webs, have had a species-wide change in feeding habits, how many other predators around the world has fishing impacted? And what role do consumers play?
"What you choose to put on your dinner plate -- that's your connection with the endangered Hawaiian petrel, and with many other marine species," Wiley said.
The research was funded by the National Science Foundation, MSU and the Smithsonian Institution.
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Story Source:
The above story is reprinted from materials provided by Michigan State University.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:
  1. Anne E. Wiley, Peggy H. Ostrom, Andreanna J. Welch, Robert C. Fleischer, Hasand Gandhi, John R. Southon, Thomas W. Stafford, Jr., Jay F. Penniman, Darcy Hu, Fern P. Duvall, and Helen F. James. Millennial-scale isotope records from a wide-ranging predator show evidence of recent human impact to oceanic food webs. PNAS, May 13, 2013 DOI: 10.1073/pnas.1300213110


Haritzalde 'Talaia' proiektuaren inguruan mintzo

Mezu hau helarazi digu Haritzalde Naturzaleen Elkarteak:

La mejora del GR121 en Mendizorrotz supondría un desastre

Haritzalde no puede aceptar este proyecto

La Asociación Naturalista Haritzalde ha solicitado oficial y formalmente al Ministerio de Medio Ambiente, a la Diputación Foral de Gipuzkoa y al Ayuntamiento de Donostia que aparquen definitivamente el proyecto de supuesta mejora del GR121, debido a los fuertes impactos que ocasionaría y a su desorbitado coste.

4 millones de euros son muchas monedas, y sobre todo en estos días donde la austeridad es mandato presidencial. 4 millones de euros va a recibir el Ayuntamiento de Donostia/San Sebastián, a cambio de “mejorar” el GR121 que transita en su municipio, en el monte Mendizorrotz. Mejorar” llama el Ministerio de Medio Ambiente (contratante en este negocio) a ensanchar y asfaltar (con gravilla) una ruta transitable que discurre por el medio con más biodiversidad del municipio, según un estudio realizado por la Sociedad de Ciencias Aranzadi para el consistorio (www.donostia.org). ¿Qué impacto en el medio natural ejercerá la obra y qué impacto en el medio ambiente tendrán los urbanitas, felices de haber colonizado otra área? No lo sabemos. Lo que sí sabemos con seguridad es que la obra aterradora no cuesta 4 millones de euros.

Nos parece mal y vergonzoso que se gasten 4 millones en algo que no lo vale, no lo necesita y tiene al lado un espacio con necesidad urgente de restauración ambiental, la Cala de Agiti.

Hay numerosas zonas que requieren de inversiones para su restauración y mejora de su estado de conservación: Motondo, cara norte de Mendizorrotz, Ulia, ribera del Urumea... Que empiecen por Agiti. Es necesario invertir en Medio Ambiente, pero exigimos se haga de una forma coherente y sensata. La costa vasca es bella y la transitan un montón de caminos vecinales que no necesitan de gravilla; sin embargo, sí que necesita dinero para su protección, para que siga siendo bella y rica, y no la ensucien con proyectos como el de “mejora” de la GR121.

Por tanto, pedimos que dicho proyecto se aparque para siempre y solicitamos que con ese dinero se inicie, para empezar, la recuperación ambiental de la cala de Agiti, lugar en el que además existió una charca en la que se reproducía la ranita meridional (Hyla meridionalis), catalogada en el País vasco “en peligro de extinción”.



Bird Fossil Sheds Light On How Swift and Hummingbird Flight Came to Be

Iturria: Science Daily

May 1, 2013A tiny bird fossil discovered in Wyoming offers clues to the precursors of swift and hummingbird wings. The fossil is unusual in having exceptionally well-preserved feathers, which allowed the researchers to reconstruct the size and shape of the bird's wings in ways not possible with bones alone.

Twelve centimeters from head to tail, E. rowei was an evolutionary precursor to the group that includes today's swifts and hummingbirds. (Credit: Photo contributed by Lance Grande of the Field Museum of Natural History)
Researchers spotted the specimen -- the nearly complete skeleton of a bird that would have fit in the palm of your hand and weighed less than an ounce -- while working at the Field Museum of Natural History in Chicago.
The newly discovered bird was named Eocypselus rowei, in honor of John W. Rowe, Chairman of the Field Museum's Board of Trustees.
First collected in southwestern Wyoming in a fossil site known as the Green River Formation, E. rowei lived roughly 50 million years ago, after the dinosaurs disappeared but before the earliest humans came to be.
E. rowei was a tiny bird -- only twelve centimeters from head to tail. Feathers account for more than half of the bird's total wing length.
To find out where the fossil fit in the bird family tree, the researchers compared the specimen to extinct and modern day species. Their analyses suggest that the bird was an evolutionary precursor to the group that includes today's swifts and hummingbirds.
Given the differences in wing shape between these two closely related groups of birds, scientists have puzzled over how swift and hummingbird flight came to be. Finding fossil relatives like this specimen is key to figuring that out, the researchers say.
"This fossil bird represents the closest we've gotten to the point where swifts and hummingbirds went their separate ways," said lead author Daniel Ksepka of the National Evolutionary Synthesis Center in Durham, North Carolina.
Hummingbirds have short wings relative to their bodies, which makes them good at hovering in mid-air. Swifts have super-long wings for gliding and high-speed flight. But the wings of E. rowei were somewhere in between.
"[Based on its wing shape] it probably wasn't a hoverer, like a hummingbird, and it probably wasn't as efficient at fast flight as a swift," Ksepka said.
The shape of the bird's wings, coupled with its tiny size, suggest that the ancestors of today's swifts and hummingbirds got small before each group's unique flight behavior came to be. "Hummingbirds came from small-bodied ancestors, but the ability to hover didn't come to be until later," Ksepka explained.
Closer study of the feathers under a scanning electron microscope revealed that carbon residues in the fossils -- once thought to be traces of bacteria that fed on feathers -- are fossilized melanosomes, tiny cell structures containing melanin pigments that give birds and other animals their color. The findings suggest that the ancient bird was probably black and may have had a glossy or iridescent sheen, like swifts living today. Based on its beak shape it probably ate insects, the researchers say.
The other authors of this study were Julia Clarke, Sterling Nesbitt and Felicia Kulp of the University of Texas at Austin, and Lance Grande of the Field Museum of Natural History.
The results will appear in the May 1 issue of the journal Proceedings of the Royal Society B.