How Pigeons Really Get Home

Homing pigeons (1)_____ for their uncanny internal compass, yet a new study reveals that sometimes the birds get home the same way we do: They follow the roads. Tim Guilford and Dora Biro at (2)_____ Oxford University followed pigeons in Oxford over a three-year period, using tiny tracking devices equipped with global positioning system technology (3)_____ by Swiss and Italian colleagues.
What they discovered was surprising. Within ten kilometers of home, the pigeons relied less on their wellknown talents for decoding the sun’s position or deciphering the Earth’s magnetic field (4)_____ them navigate. Instead they opted for a habitual route that followed linear features in the landscape, such as roads, rivers, railways, and hedge lines — even when it wasn't the most direct way home. “It was almost comical,” says Guilford. “One pigeon followed a road to a roundabout, then exited onto a major road that led to a second roundabout. Others flew down the River Thames, only to make a (5)_____ turn at a bridge.” Guilford suggests that sticking to a (6)_____, linear route may actually make homing more reliable — and easier. “It made me smile to see it,” says Guilford. “You can imagine yourself flying along a road doing the same thing.”

Why Does Red Mean Stop?

The 19th-century Scottish engineer Robert Stevenson, who was active in designing early lighthouses, (7)_____ for an alternative colour to white — most lighthouses had a white beacon — when he built a lighthouse near to one that already existed, because he was afraid ships (8_____) be able to tell which was which.
Of the light sources and (9)_____ glasses available at the time, he found that red was a particularly intense light, meaning it (10)_____ from the greatest distance. So in maritime signalling red became an alternative to white, and was later adopted by the Admiralty in 1852 (11)_____ the port-side on steam vessels. Green was adopted for the starboard-side, and vessels seeing the green light on other ships had the right of way.
When train tracks were developed, engineers adopted this system as (12)_____ stop and go — and the same system continued with cars.