January 20, 2014

The long-held theory that birds fly in a V formation to conserve energy has been confirmed scientifically by researchers tracking migrating northern bald ibises. The researchers found that each bird beyond the first adjusts its position and the beating of its wings to get a helpful lift from the bird in front. For the study, published in the journal Nature, the scientists attached sophisticated sensors to the birds.

Flocks of many larger birds, including geese, ducks, and pelicans, adopt V-shaped formations for long migration flights. Scientists have long suspected that this helps them save energy, but the study provided the first scientific confirmation.

Some of the scientists behind the study were involved in a program to release captive-bred ibises into the wild. They trained the birds to migrate by getting them to follow a lightweight aircraft. The scientists attached a sensor pack to each bird for a 600-mile (965-kilometer) migration flight from Austria to Tuscany. Each pack included an accelerometer, a gyroscope, a magnetometer, and an extremely sensitive Global Positioning System (GPS) unit. This setup enabled the scientists to track each bird’s speed, position, and wing rhythm in detail. The scientists then compared the data to models developed using aerodynamics, the study of movement through air and other fluids.

Canada geese and other birds that migrate in a flock fly in a V formation to help save energy on long flights. (© Chase Swift)

The results showed that each bird positioned itself to take advantage of vortices (swirls of air) generated by the wings of the bird in front. The vortices are created when the wings push down the air. In the process, other air rises to the right and left of the wings. The birds positioned themselves to get the maximum upward push from these swirls. Likewise, each bird timed its wing beats to take the greatest advantage of vortices, adjusting its rhythm whenever its position changed.

Taking advantage of such vortices makes each bird’s flight slightly easier. Such energy savings may be small, but they can add up over long migrations. The birds in front gains no advantage, but the ibises in the study changed leaders from time to time, enabling each bird to enjoy the added lift.

January 15, 2014

Stocks of incandescent light bulbs dwindled in January 2014 as manufacturers ceased production of 40- and 60-watt lamps. These wattages joined 75- and 100-watt incandescents in light-bulb limbo. They were phased out of production in 2012 and 2013, respectively. The phase-out was the result of the Energy Independence and Security Act signed by President George W. Bush in 2007. The regulation does not outlaw the sale or use of incandescents, but it restricts companies from manufacturing or importing them.

Incandescent lights bulbs, the oldest kind of light bulb, produce light by passing electric current through a metal wire called a filament. The filament heats up and glows. But in the process, about 90 percent of the electric current’s energy goes to waste as it turns to heat. The Energy Independence and Security Act aimed to reduce such waste.

An incandescent light bulb was the first kind of light bulb invented. It uses a thin metal wire called a filament. Passing an electric current through the filament causes it to glow. © Michael Germann, Shutterstock

Newer electric lights, including compact fluorescent lights (CFL’s) and light-emitting diodes (LED’s), are more expensive than incandescents, but they last much longer and waste far less electric power. Savings from reduced electric bills often make these more efficient light bulbs cheaper, in the long run, than incandescent bulbs. Using more efficient light bulbs also leads to less pollution from power plants that burn fossil fuels.
While some early CFL’s cast a harsh-colored light and flickered upon turning on, modern CFL’s and LED’s turn on smoothly and can mimic the type of light produced by incandescent bulbs. Even so, some customers rushed to hoard 40- and 60-watt incandescents before they disappeared from store shelves permanently.

Additional World Book articles:

• Lamp
• Lighting
• Light pollution
• Choosing the Right Light

March 15, 2012

The area covered by trees in many United States cities is declining, reports the U.S. Forest Service, and that loss of trees–as many as 4 million annually–translates into an astronomical loss in energy efficiency. According to the Forest Service, urban trees greatly decrease heating and cooling costs, by as much as $2,500 over the lifespan of a mature tree; improve air and water quality; and help control water drainage and erosion. The Forest Service calculates that the financial loss of an urban tree is, thus, three times greater that the cost of maintaining it.

Forest Service researchers David Nowak and Eric Greenfield arrived at their conclusion by comparing aerial photographs of 20 urban areas from the years 2002 to 2010 and evaluating the differences in the canopy coverage. They found that the tree cover in 17 out of the 20 cities had declined. New Orleans, Louisiana, had the largest decrease. (The research suggests that much of the tree loss there was a result of Hurricane Katrina in 2005.) Only one of the 20 cities–Syracuse, New York–showed an increase in the amount of tree cover.

Many urban trees are lost to the artifically made objects in a designed landscape. This is known as “impervious cover,” which includes rooftops and pavement–streets, sidewalks, and parking lots.

Trees across North America are under attack by a number of different diseases and pests. Urban trees are especially threatened by the emerald ash borer, the Japanese beetle, and a number of fungal diseases, including the Dutch elm disease.

Ginkgo trees are popular for city plantings because they are largely resistant to air pollution as well as various tree diseases. (Atoz)

Tree-planting programs in many cities have helped to slow tree loss but have not been able to reverse the larger trend. In an effort to make city planning more tree-conscious, the Forest Service is providing cities with a free software program entitled i-Tree Canopy. The program lets users analyze changes in an area’s tree coverage by pairing aerial photographs from different time periods. U.S. Forest Service Chief Tom Tidwell hopes the tool will help communities plant and maintain trees more effectively.

Additional World Book articles:

• Conservation
• Green building
• Ecology
• Trees Under Threat (a special report)