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biology 0610printed 255 · PDF 255
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A study was carried out in Sweden into the effects of natural selection on wing length in
reed warblers.
The wings of young reed warblers reach their maximum length a few days after leaving the
nest.
At this age the wing length in millimetres of each bird was recorded. Each bird was
identified by putting a small ring around one of its legs.
When the birds were caught in net traps as adults, the information on the rings was used to
identify specific birds and their ages.
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