Defenders Magazine

Wild Life: The Great Tit's New Tweet

© Kim Taylor/NaturePL.com

The Great Tit's New Tweet

Is that hip-hop coming from the treetop? Scientists listening to great tits think so. According to a new study published in Current Biology, birds in urban areas tweet more brashly, using staccato notes at a higher pitch, than forest dwellers. Researchers believe this to be the equivalent of avian hip-hop, which birds may have adapted so they can hear each other above the din of the city.

Researchers at the University of Leiden in Norway monitored great tits—a common European songbird—in 10 cities, including Amsterdam, London and Prague. In all 10 places, they found that city birds sing faster, start their phrases with shorter notes and leave out lower frequency notes compared to individuals of the same species living in surrounding forests.

The sounds of city and country great tits are so different that the researchers believe that eventually the birds could divide into two distinct species. But other birds might not be so lucky, says biologist Hans Slabbekoorn, who led the study. Birds use song to attract mates and define territory. If other species can't adapt to be heard above the noise, they could disappear from cities altogether.

Lessening to Prozac

Happy pill though it may be, Prozac may actually be depressing wild mussel populations in North American rivers. A new study shows that exposure to the anti-depressant disrupts the mollusks' reproductive cycles, potentially increasing their risk of extinction.

In one of the first studies to examine the impact of anti-depressants on mussels, scientists found that acute exposure to high concentrations of Prozac in a lab caused female mollusks to release larvae before they were able to survive on their own.

Like many prescription drugs, fluoxetine, the active ingredient in Prozac, ends up in streams and rivers because sewage treatment facilities lack the capability to completely remove the drugs from wastewater.

"The results from this study were quite alarming," says Rebecca Heltsley, a biologist at Hollings Marine Laboratory in Charleston, South Carolina, who worked with researchers from North Carolina State University on the study. "It's a big concern because freshwater mussels are already such an imperiled group."

About 70 percent of the nearly 200 native North American mussel species are extinct, endangered or declining, she says, crowded out by invasive species such as zebra mussels, devastated by sedimentation and habitat loss and poisoned by pollutants. "The presence of fluoxetine and similar drugs that increase serotonin levels in U.S. rivers and streams has likely compounded the problem," Heltsley adds.

Freshwater mussels play a key role in the ecology of rivers and streams by filtering large volumes of water every day. In doing so, they remove contaminants and excessive nutrients from the water and serve as an early warning sign of water-quality problems. They are also an important source of food for otters and fish.

Warming by the Numbers

90 Percent of certainty that humans are the main cause of global warming.
United Nations Intergovernmental Panel on Climate Change, January 2007

50 Percent of people who think global warming is caused by human activities.
AC Nielsen, January 2007

57 Percent of people around the world who consider global warming a "very serious problem."
AC Nielsen, January 2007

13 Percent of Americans who have never heard of global warming.
AC Nielsen, January 2007

44 Percent of global warming emissions that are a direct result of individual—not corporate—behavior.
Society for Conservation Biology

20 Pounds of carbon dioxide kept out of the atmosphere each time one person opts to save a gallon of gasoline.
Union of Concerned Scientists

2.2 Degrees F warmer 2006 (the hottest year on record in the United States) was, on average, than 1998 (the previous record-holder).
National Climatic Data Center

A Right Turn for Lobstering?

Doing right by right whales turns out to benefit lobstermen as well, according to recent research in Canada.

Despite 70 years of protection, the large, slow-moving North Atlantic whales remain critically endangered because of ship strikes and entanglement in fishing gear—predominantly lobster traps that are tied to the surface via a buoy line.

Since 2002 commercial fishing gear has seriously injured or killed six right whales, according to the Ocean Conservancy, which filed suit against the National Marine Fisheries Services in February to try to force the agency to protect the 300 or so whales that are left in the North Atlantic.

Canadian researchers compared lobster fisheries in Nova Scotia, where fishing is restricted to the winter season, with those in Maine, where it is permitted year-round. They found that lobstering in Canada turned the same profit with fewer whale deaths, less work and 88 percent fewer traps. Although the U.S. fleet catches a third more lobsters, it uses more resources, is less efficient and more costly.

The biologists suggest the United States switch to a six-month lobster season and reduce the number of traps set by 90 percent. They also point out that limiting lobster traps along the Gulf of Maine in the spring and fall would allow the whale a safe migration while not affecting the livelihood of lobstermen.

"This is a classic win-win situation," says Boris Worm, a biologist at Dalhousie University in Nova Scotia, and one of the authors of the study. "Given the high fuel and bait costs lobstermen incur, a shorter season with fewer traps will actually save money."