Pat Shingleton: "Spring is for the Birds!"
Very soon, the swallows will return to Capistrano and the buzzards will arrive in Hinckley, Ohio. Many of our viewers and readers report on the visiting purple martins in Baton Rouge. At 4:58 PM Wednesday, March 20th, Spring sprang. The official time for the start of Spring is determined by the earth's motion around the Sun. Sky and Telescope provides some interesting items on the start of Spring. For the Northern Hemisphere it's defined as the moment when the Sun passes over Earth's equator on its journey north, officially called the vernal equinox. The word, equinox, originates from the Latin for "equal night." Day and night are not exactly 12 hours long at equinox for a couple of reasons. Sunrise and sunset are determined when the Sun's upper edge, not the center, crosses the horizon. The second reason involves the Sun's position near the horizon, causing refraction by the Earth's atmosphere which shifts its position slightly upward. A resident bird watcher convinced me that when we experience our last robin, in South Louisiana, get ready for the heat. It was once believed that homing pigeons relied on the sun’s position to decipher Earth’s magnetic field for navigation. Years ago, researchers at Oxford University used tiny tracking devices, equipped with global positioning systems, to track pigeons over a three year period. They discovered that within ten kilometers of home, the pigeons followed roads, rivers, railways and hedge lines, even when it was not the most direct path home. Scientists believe the birds consistently followed a memorized route.