Newswise — Just call them "Renaissance birds." Cormorants can fly like ducks, swim like penguins, dive like seals, and catch fish with the greatest of ease. How are these large, voracious birds able to do it all " swim, dive, fish and fly " like no other bird?
To answer this question, researchers from the Technion-Israel Institute of Technology are using trained cormorants, underwater cameras and computer analysis to study the secrets behind these birds' unique abilities. By doing so, they also hope to find a practical way to alleviate the rising cormorant-fishermen tensions around the world.
Such tensions are the result of the competition between humans and the cormorants for the same prize: fish. Current solutions include culling of the birds' numbers. The State of Minnesota, for example, killed 2.200 cormorants in May of 2005, and some European countries cull tens of thousands of cormorants per year. The Technion researchers, however, hope that unlocking the secrets of the birds' physiology will help develop more peaceful options to the conflict.
The scientists hope to develop practical "win-win" solutions that benefit fishermen and cormorants alike by examining the cormorants' behaviors, needs, abilities and limitations in the context of the ecological conditions that exist in affected areas.
"We learned that besides their outstanding flying abilities, cormorants can dive down to depths of 30 meters in search of food and can stay underwater more than two minutes," says lead researcher Gal Ribak. "We are trying to understand how birds built for flight are able to function so well underwater and become underwater predators that live on fish."
The cormorants used in the study, trained from the time they were hatched, were taught to swim from point-to-point in an underwater canal. The researchers videotaped the birds as they swam and used computer programs to analyze their swimming motions and styles. What the researchers found was so unique that it took a blend of biology and aerospace engineering to decipher.
"Similar to the way an airplane creates uplift in order to keep it in the air, cormorants create negative lift, which enables them to dive," explains researcher Prof. Zeev Arad of the Faculty of Biology. "In effect, cormorants have found the golden mean between penguins and ducks. The penguin gave up on flight in favor of diving. The duck flies well but dives poorly. The cormorant excels at both."
The researchers also found that cormorants integrate gliding while swimming underwater. They do not swim continuously, but instead glide after each leg flap. This form of swimming, say the researchers, uses at least 30% less energy. They also dispelled the common notion that the cormorants' diving abilities come from feathers that, when wet, reduce the bird's buoyancy. On the contrary, the cormorants' feathers actually function as a wetsuit, and keeping them dry provides them with essential insulation in cold water. This explains why these birds can so often be seen perched with wings spread in an attempt to dry them. Area Fishermen Support Research
The study is being conducted with the full cooperation of Israel's Nature and Parks Authority (NPA) and fishermen and fish farmers in Northern Israel's Hula Valley, one of the world's premier bird-watching regions and a prime wintering spot for many bird species. The fishermen " like their counterparts in the United States and the world over " have an especially strong interest in the research; they contend that the birds eat hundreds of tons of fish, making them a threat to commercial fishing and fish farming.
More than 20,000 cormorants live in Israel for five months each year. But while the cormorants congregate and roost in the Hula Valley, they actually prefer to fish about 20 miles away, in the Sea of Galilee, where the water is clearer. The researchers say that " despite their voracious appetites " cormorants are very picky eaters, and the clearer water in the Sea of Galilee enables them to better distinguish between the fish they catch.
"Our understanding of the cormorants' food preferences and underwater visual capabilities allows us to "lead" the cormorants to preferred sites with confidence that they will find what they need," says Arad. "This ensures that we are not compromising the birds' needs. Meanwhile, the fishermen see the practicality of our means, since we're able to show the fishermen hard data about its positive effects. They have actually become collaborators in the general policy, which is a very important step in solving nature conservation-human conflicts."
Over the last three years, he says, the Hula Valley area fishermen and the NPA have successfully used a "scaring technique" that utilizes cell phones, a coordinator and fireworks to lead the cormorants to feed only in the Sea of Galilee. Competition between cormorants and area fishermen and fish farmers has been reduced so dramatically that some fishermen have asked for cormorants to be "brought back." (Arad says the biggest reason the birds are missed is because they serve as natural predators of a number of unwanted "pest" fish species.)
The findings are being published in Ribak's doctoral dissertation under the guidance of Prof. Arad and Prof. Danny Weihs of the Faculty of Aerospace Engineering. The trio is also collaborating with the Israel Nature and National Parks Protection Authority to design a new and improved research facility in the Hula Reserve to study water birds and aquatic animals. The researchers say their work has implications for areas around the world struggling with cormorant populations. The European Community has already established a 24-country task force called INTERCAFE (Prof. Arad is an Israeli representative) to work on possible solutions to this conflict. Using the Hula Valley as a test case, Arad will host an international conference for the group in January 2006.
The Technion-Israel Institute of Technology is Israel's leading science and technology university. Home to the country's only winners of the Nobel Prize in science, it commands a worldwide reputation for its pioneering work in nanotechnology, computer science, biotechnology, water-resource management, materials engineering, aerospace and medicine. The majority of the founders and managers of Israel's high-tech companies are alumni. Based in New York City, the American Technion Society is the leading American organization supporting higher education in Israel, with 17 offices around the country.
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