Date: Fri, 7 Dec 2001 12:27:37 -0500 Reply-To: Maryland Birds & Birding Sender: Maryland Birds & Birding From: Denise Ryan Subject: Muscle Mass in Birds MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=ISO-8859-1 Your question about muscle mass reminded me of an article I just read the end of October about migration and fat. I thought the group might find it interesting. Apparently large amounts of fat makes Red Knots more efficient and is worth the weight for flying during migration. If only that were true for all of us! You can read the article from the Journal Nature at this link or below. http://www.nature.com/nsu/011018/011018-10.html Swimming after a heavy meal may not be wise - but flying is another matter. Birds fly more efficiently when loaded with food, new research suggests, helping to explain how they can migrate thousands of kilometres without stopping. And a second study has confirmed the century-old suspicion that birds fly in a V formation to save substantial amounts of energy. Anders Kvist at Lund University in Sweden and his colleagues looked at flying efficiency in red knots, small waders that double in size for their annual migration from Siberia to Africa. Fully fed, red knots flying in a wind tunnel for 6-10 hours extracted significantly more power from each unit of food. This might help to explain why birds often make long non-stop flights even when they don't have to cross an ocean or desert, says Kvist. "Since efficiency increases when the birds are heavy, it might not be as bad to make long flights as people thought." The research flies in the face of computer predictions that birds are less efficient when full. Says bird aerodynamics specialist Jeremy Rayner of the University of Leeds: "It's a major advance, because it has disproved something we've held on to for a long time." The finding is "extremely unexpected", agrees John Speakman who works on animal energy use at the University of Aberdeen. "This changes our whole view of migrational strategies in terms of how much fat birds should deposit to cross, say, the Sahara Desert." Understanding the relationship between food and flight might help ecologists to measure the impact of habitat change on migratory birds, Speakman says. "If you're deciding whether to flood an estuary, for example, this could help you make more sensible predictions about how it will affect birds that use the estuary as a stopover." It is unclear how birds increase their efficiency when migrating, Kvist says. Puzzlingly, they don't adopt the most economical strategy at all times. Kvist speculates that when birds are breeding they may keep reserves of strength for sudden manoeuvres such as speeding up or swerving to avoid a predator. Birds also conserve fuel by flying in V formations. By measuring heart rates, researchers in France now have proof that pelicans use 11-14% less energy flying together, even when they are not perfectly positioned to take advantage of the wake from those in front of them. Configured flight may create a stream of air that allows birds to glide longer, suggests Henri Weimerskirch, the biologist at the National Centre of Scientific Research at Villiers en Bois, who led the study. "If you look closely, you see that the birds at the back are gliding more than the leader." People have been asking whether V formations are more efficient for more than 100 years, Speakman says, but no one had measured energy savings before. "They took a century-old problem and went to the heart of it," he says. References Kvist, A., Lindstrom, A., Green, M., Piersma, T. & Visser, G. H. Carrying large fuel loads during sustained bird flight is cheaper than expected. Nature, 413, 730 - 732, (2001). Weimerskirch, H., Martin, J., Clerquin, Y., Alexandre, P. & Jiraskova, S.. Energy saving in flight formation. Nature, 413, 697 - 698, (2001). =A9 Nature News Service / Macmillan Magazines Ltd 2001 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D To leave the MDOsprey list, send e-mail to listserv@home.ease.lsoft.com with the following message in line 1: signoff mdosprey =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =========================================================================