Herring gulls in NYC also drop clams on rocks. Maybe they will get a lot better at it now that the Staten Island dump is closing! Allen Aige [log in to unmask] On Mon, 29 Jan 2001 11:56:04 -0500 Sarah Watson <[log in to unmask]> writes: > Gulls Find New Way To Eat Clams > > By SONJA BARISIC > .c The Associated Press > > > JAMESTOWN, Va. (AP) - The herring gull scoops a clam out of a muddy > creek, > flies 200 yards to a road, rises a few feet higher, opens its bill > and bam! - > the clam hits the pavement. > > That scene is repeated, sometimes hundreds of times a day during the > winter, > as herring gulls on Jamestown Island near Williamsburg use the road > to crack > open the hard shells so they can retrieve and eat clam meat. > > ``They are quite resourceful,'' said Daniel A. Cristol, an assistant > professor of biology at the College of William and Mary, who has been > studying the gulls for five years. > > ``The long-term question is: How do they get good at it?'' Cristol > said as he > stood along the road, watching the gulls on a bracing, sunny day. > ``Is it a > learned thing, or is it something that evolved long ago, somewhere > else, and > they just appropriated it here?'' > > Cristol said the skill could be innate, but his preliminary findings > suggest > that the behavior is consistent with learning - an example of how > some > animals are able to adjust their lifestyles when people alter their > habitats. > > Of the five species of gulls present on Jamestown Island during the > winter, > only herring gulls drop clams. > > ``I think herring gulls have the capacity to learn how to do it and > the > others don't,'' Cristol said. ``They learn it from one another.'' > > The gulls do this about two hours a day during low tide, from late > November > through late March. > > They use the road leading to Jamestown Island, which is littered > with pieces > of clam shell, and also the hard surface of a small island in the > creek > believed to be the remains of a Civil War-era bridge. The road is > better, > though, because too many gulls - including the other species - lie > in wait on > the bridge, ready to steal the meat when a clam is dropped. > > Cristol and his students collected and measured about 6,000 clam > shells over > three years, and it appears that the gulls favor a middle-sized > clam, about 3 > inches across. > > Cristol speculates that a small shell isn't worth the energy > required to drop > it because it doesn't contain much meat, while a large clam is > meatier but > too heavy to carry. > > Cristol also has noticed that the gulls usually rise up in the air a > few feet > before they drop the clams. He thinks they are trying to reach the > most > efficient dropping height. Too low, and the clam won't break; too > high, and > the bird is wasting energy. > > The birds seem to get better at gauging the right clam size and > height as > they age, Cristol said. > > Cristol did similar research with crows and walnuts in California > when he was > a postdoctoral fellow at the University of California, Davis. > > Crows were dropping walnuts onto roadways, and some people thought > this was > an intelligent act because it looked like the crows were > deliberately using > moving vehicles as nutcrackers. > > Cristol and fellow researchers observed hundreds of crows and > concluded that > the birds were simply dropping nuts onto any available hard surface > to try to > break them open. > > Still, Cristol wondered if the crows had inherited the dropping > technique or > learned it from other crows. He brought that question with him when > he came > to William and Mary in 1996 and continued his research with herring > gulls. > > In a way, the gulls are better to study because their age can be > determined > by the color of their plumage, which changes from brown to white. > Crows > remain the same color. > > ``If he can age the gulls, he can track how gulls learn, or at least > get > started on that,'' said Peter Smallwood, a behavioral ecologist and > assistant > professor of biology at the University of Richmond. > > ``His ability to age the gulls can help in trying to understand how > do gulls > get so good at this,'' Smallwood said. ``Is it instinctual? Are they > able to > use their experience to hone in on it by trial and error, or do they > learn > from each other?'' > > Cristol wonders whether the gulls have a mechanism for learning by > observing > other members of their species. Only a few instances of such > so-called > ``social learning'' have been documented. > > One of the most famous examples is that of the Japanese macaque > monkeys, also > known as snow monkeys. In the early 1950s in Japan, researchers gave > sweet > potatoes to a group of macaque monkeys. Imo, a young female, washed > her > potato in a stream before eating it. > > Other monkeys began washing their potatoes as well, and today, > potato washing > among the monkeys is common. Some think that proves that the animals > can pass > their cultural traditions to new generations. > > On the Net: > > Cristol: http://www.wm.edu/biology/Cristol.html > > U.S. Geological Survey, on herring gulls: > http://www.pif.nbs.gov/bioeco/herrgull.htm > > *~*~*~*~*~*~*~*~*~*~*~*~*~*~ > Sarah R. Watson > Curatorial Assistant > Dept. of Malacology > Academy of Natural Sciences > *~*~*~*~*~*~*~*~*~*~*~*~*~*~ > http://www.geocities.com/scalaria