The New Scientist reports on study showing that penguins with wing band ID's don't breed as well as others. I'd always thought those bands looked pretty huge, but apparently they don't interfere with range of motion. They do add noticable drag, though; and when life or death depends on swimming fast. . . Most banded penguins seemed to survive as well as the others, but not have the extra energy needed to breed.
The French team used an alternative tracking method--microchip transponders--and compared penguins with both with penguins with only the transponders. Apparently seals aren't as bothered by the small amount of drag--a UK group says they don't see any problems.