A resident bird watcher convinced me when we experience our last robin in south Louisiana, get ready for the heat. The traditional swallows have returned to Capistrano, the buzzards have arrived in Hinckley, Ohio, and we’re on the lookout for purple martins. As noted in a previous column, it was once believed homing pigeons relied on the sun’s position to decipher the Earth’s magnetic field for navigation. Years ago, Oxford University researchers used tiny tracking devices, equipped with Global Positioning System devices, to track pigeons over a 3-year period. They discovered that within 10 kilometers of home, the pigeons followed roads, rivers, railways and hedge lines, even when it wasn’t the most direct path home. Scientists believe the birds consistently followed a memorized route. Fastcast: Comfortable.