Soon the renewal of spring will begin. Snow on the woodland floor will be replaced with fresh emerald leaves and then a quilt of vernal flowers. Ice-covered streams and wetlands will melt, and hundreds of spring peepers will sing in lengthening evenings. In those same wetlands the cold groan of wind will be replaced by the raucous tee-err of red-winged blackbirds. Red-wings are the drum majors of the migratory parade of birds that will stream into area wetlands, fields and forests to meet, mate and raise families. Have you ever wondered why birds migrate in the first place, why they leave in the fall and come back in the spring, where they go for the winter and how they find their way along the journey back and forth• The first question is easy. Most of the birds that migrate are going to other places to ensure a good food supply. For example, in the winter, when food - such as insects - is gone because of the cold, the birds that rely on insects for food fly south to warmer areas that have abundant food. Likewise, waterfowl and wading birds that feed in shallow water move south, away from ice-bound streams, rivers and lakes to open water and adequate feeding grounds. Where do the birds go• Some move only far enough south to avoid the worst of the winter weather. The southern United States, especially along the Gulf Coast, is the home for many species that spend the summer here. Others go further and spend their winter in Central and northern South America. Along the northern edge of South America, several mountain ranges rise precipitously at the edge of the Caribbean Sea. Here the warm, wet winds off the water are forced upward into cooler air, and their moisture is wrung out in the form of clouds. The forests of the upper mountains are dense tangles teeming with life. Massive trees covered with ferns, epiphytes, and orchids stand on the steep slopes. Below the canopy, the growth is dense with a myriad of plants that stay green throughout the year. In this riot of green, insects are plentiful. In that abundance, many of the birds that make western Pennsylvania their summer home spend their winters. Because of this yearly influx, the coastal ranges of Columbia and Venezuela have the highest densities of bird species in the world. Northern species mingle with the birds of the tropics, and during our winter the cloud forests are home to more than 500 bird species in each square kilometer. For even the casual birdwatcher this assemblage is overwhelming. Familiar species include northern water thrush, turkey and black vulture, black and white warbler and barn swallow. These exist alongside tropical exotics such as macaws, an array of tanagers, humming birds and parrots.

Migration studies have demonstrated that many birds use different routes during the fall and spring travels. On their way south the birds flow to the southern United States along the Gulf coast and Florida then cross water, hopping from island to island, finally arriving in northern South America. On the return trip, the birds stream from the South American interior to the coast, then take a land route through Central America, Mexico and Texas and then spread out over North America. In the spring, the Gulf of Mexico's northern coast experiences great waves of migrants arriving almost daily between mid-April and early May. Researchers have used radar to calculate that 30,000 songbirds cross each mile of coast between Lake Charles, La., and Corpus Christi, Texas, every hour for five hours during such a wave. On both journeys there are perils. Storms and erratic winds may sap a bird's energy, and it may not be able to cross long stretches of water. Predators are waiting in every habitat along the way. Finally, human created obstacles like communication towers and degraded habitats, which lack the necessary food supplies, may bring an early end to the travels of an individual bird. Fortunately many birds can alter their food preferences on a moment's notice to meet the energy demands of migration. Insect-eating species can switch to a fruit-rich diet to fatten up in a hurry for the trip. How the birds accomplish the passage from one continent to another is the most difficult question to answer. One of the astonishing aspects of the feat is the energy efficiency of birds. Studies of the fall migration of blackpoll warblers, from Nova Scotia to South America, have found that the birds lose half their weight in the four-day-and-night, 2,400-mile flight. This is equivalent to a fuel efficiency of 720,000 miles a gallon. Equally amazing is the navigation skills of these tiny creatures. Recent experimental work has indicated that birds have an inherent ability to use the position of the sun by day and the stars by night to chart their courses over land and water. What is puzzling is that individual birds have the ability to not only travel great distances, but they are able to find their way back to exactly the same territory or same tree that they occupied the year before. Considering the why and how of bird migration is fascinating, but when I think of the results - of the return of the red-wings, the warblers, and others to the region - only one thought comes to mind ... Welcome back. Paul g. Wiegman is a writer, educator, photographer and naturalist who works with a number of local and state organizations. Write to him c/o Tribune-Review, 622 Cabin Hill Drive, Greensburg, PA 15601; or e-mail him at pwiegman@ix.netcom.com .

Copyright ©2025— Trib Total Media, LLC (TribLIVE.com)