For decades scientists have been following penguins by putting bands around their flippers. This allows individual birds to be identified at a distance. But there have been concerns that flipper bands might harm the birds by slowing them down as they swim.

The latest study, reported in the journal Nature, confirms it. Scientists from Strasbourg University followed a colony of king penguins for ten years. Birds fitted with bands died younger, started breeding later in the year, took longer to forage for food, and overall raised about 40% fewer chicks.

The researchers suggest that using flipper bands would now be unethical in most situations. Scientists in the field will now have to find other tagging methods, but in the meantime there are also concerns that some data gathered on penguins down the years, in this ecologically crucial part of the planet, may now be worthless.

Richard Black, BBC News

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bands

here, tags which are attached to the penguins to identify them

flippers

penguin's wings, which are used for swimming instead of flying

concerns

worried feelings

harm

hurt or injure

colony

here, a large group of penguins which live together in one place

breeding

reproducing

forage

search their surroundings

chicks

very young penguins

unethical

not following widely held moral beliefs

worthless

of no real use or value