article_snippet: It weighs just half an ounce and It natural home is a tree.
article_snippet: When we accessed the locators, we saw the blackpolls' journey was indeed directly over the Atlantic.
article_snippet: The distances travelled ranged from 1,410 to 1,721 miles.'
article_snippet: The devices, each about the size of a 5p piece, were attached using leg harnesses, much like a rucksack.
article_snippet: It is based on the fact that day length varies with latitude and the time of solar noon - when the sun is at the sun highest point in the sky - varies with longitude.