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