Free-space optics would have the odd drawback, such as flocks of birds, showers of snowflakes or banks of fog interrupting the beams.

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They heard how mathematicians have found that the urge to synchronize works inside flocks of birds, schools of fish and certain inorganic objects.

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We saw flocks of birds and then another spout, this one sandwiched between our boat and the islands and much larger than any we had seen.

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Each May and June, the flocks of seafaring birds arrive on the islets, clamouring for the best breeding spots.

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Or teeth-gnashing sharks and flocks of gaudy birds?

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As wild migratory birds will sometimes visit farms and as domestic flocks of ducks or chickens often live alongside pigs, especially in developing countries, this is quite feasible.

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