SCIENCE

Notebook

To Get Fed, Some Birds Wing It

Nature generally frowns on scorched-earth policies. Consider the cuckoo, which slyly lays its eggs in the nests of other birds. Upon hatching, a young cuckoo kicks out the other chicks and eggs to reduce competition for food. But there is a downside to that degree of greed: less cheeping in the nest, which generally results in less ambitious provisioning by adults.

Some kinds of cuckoos make up for this setback by cheeping as frequently and as loudly as an entire nest full of chicks, triggering intensive feeding behavior by their adoptive parents. Now scientists have identified a different trick used by another kind of cuckoo.

Horsfield's hawk-cuckoos of East Asia do not cheep much, but they do flap their wings a lot when begging for food. Keita Tanaka and Keisuke Ueda of Rikkyo University in Japan wondered whether the yellowish, beak-colored patch under the hawk-cuckoo's wings might be tricking the adults into providing more food by making them think there are more beaks in the nest.

In one experiment, the researchers showed that the cuckoos are more likely to expose the color patch under their wing the longer they've gone without a meal, suggesting they are using the visual cue as a tool for getting more food. In a second experiment, the scientists painted over some of the cuckoos' patches with dark dye. They found that those birds got fed less.

At times the adults even poked food at the wing patches.

These cuckoos may use visual cues instead of auditory ones because they typically target birds that nest on the ground, where extra noise might attract predators, the researchers theorized in the April 29 issue of the journal Science.

-- Rick Weiss

Gulf Coast Dead Zone Is Early

The "dead zone" in the Gulf of Mexico -- an area that forms every year where much of the aquatic life has died -- has begun to appear much earlier than usual, indicating it may be larger than in the past, researchers have reported.

A team of scientists from Texas A&M University, Texas A&M at Galveston, Louisiana State University and NASA recently surveyed the area in the northern Gulf of Mexico where the zone has been appearing, and found the water contains lower oxygen levels than expected this time of year.

The dead zone, located where the Mississippi and Atchafalaya rivers empty into the Gulf, typically develops in late spring and early summer following the spring flood stage of the rivers, which bring large amounts of nutrients into the Gulf. The high levels of nutrients cause blooms, or sudden growths, of phytoplankton. When the creatures die and sink to the bottom, their decomposition strips oxygen from the water, creating inhospitable conditions for other marine life.