OUTDOOR CORNER: NEOTROPICAL BIRDS BEGIN TREK BACK TO SUMMER HOMES

It's that exhilarating time of the year again. The landscape is burgeoning with new life, inviting those who love springtime to immerse themselves in the natural world. Spring is also a time when North Americans welcome back countless flocks of Neotropical migratory birds that pass through or come to stay for the summer in our gardens, fields and forests.

Neotropical migratory birds -- ones like the Ruby-throated Hummingbird, Red-eyed Vireo, Scarlet Tanager, or any of the several warblers -- spend only a third of their lives in the United States or Canada. The rest of the time, they live in tropical regions of Mexico, Central and South America, the Caribbean Islands, or areas en rote between their summer and winter homes.

Many of our Missouri resident birds, like the chickadees, nuthatches and woodpeckers simply prefer to stay in the same general areas year-round. Some of the nearly 200 species of Neotropical birds travel thousands of miles twice a year!

Migration in North America is essentially north-south along four principal routes or "flyways" -- Pacific, Central, Mississippi and Atlantic. Different species characteristically migrate different distances between wintering and breeding areas. The question of how birds find their way between breeding and wintering grounds has puzzled people for as long as they have been aware of the phenomenon of migration. Today we know many more parts of the puzzle's solution than we did even 25 years ago.

In order to travel over thousands of miles between breeding and wintering sites, not to mention find their way back to precise nesting or roosting sites, birds mut be able to orient (determine compass direction) and navigate (judge their position while traveling). The short explanation of this complex migration phenomenon is that birds find their way by using a variety of cues in a hierarchical fashion. Different species may use these cues in different orders of priority, and some cues may always be used in preference to others.

Birds acquire directional information from five primary sources: (1) topographic features like mountains, rivers, tall buildings, ect., including wind direction which can be influenced by major land forms, (2) stars, (3) sun, (4) Earth's magnetic field and (5) odors.

The Missouri Department of Conservation is concerned about problems facing Neotropical migrants because so many of them nest in, as well as pass through, our state along the Mississippi flyway. Declining bird populations have been associated with environmental problems since the 1960's when Peregrine Falcons (a Neotropical migrant), Bald Eagles, Ospreys, ect., suffered losses from the pesticide DDT, a problem that still persists in tropical countries.

It wasn't until the 1970's that a few biologists in the eastern U.S. noticed that some of their favorite songbirds had become scarce in areas where previously they were common. Additional evidence of declining populations comes from breeding bird surveys conducted annually since 1966, providing data to document that 54 percent of our Neotropical migratory bird species declined between 1980 and 1989.

Radar stations detect and map bird migration as they move across the Gulf of Mexico each spring. Scientists have examined records which reveal the number of flights, and presumably the number of birds, decreased during the 1980's to about half of what they were in the 1960's.

Birds are not the only wildlife species that migrate each year and suffer declines. Certain bats and butterflies share many of the problems birds face. The very nature of migration exposes these animals to serious hazards.

Many species are losing breeding habitats in North America and wintering habitats in Central and South America. Habitat fragmentation and modern land uses are causing many species to suffer much greater levels of predation and nest parasitism than what occurred historically. Once again, the disappearance of birds is telling us something is wrong.

When summer finally arrives, the trees in our backyards and forests will be alive with breeding birds. Their cheery calls and melodic serenades constantly remind us that this is the best time of year to appreciate these wonderful songsters -- not just for themselves alone, but for the incredible role they play in helping to keep our trees and shrubs healthy.

Not all birds eat insects, but the majority do. Some species eat as many as 300 insects a day during the summer months. A breeding pair of Neotropical migrants can devour 25,000 to 50,000 caterpillars and other insect pests just in the period it takes them to raise a family!

To slow declines in populations of Neotropical migratory birds, the National Fish and Wildlife Foundation and other international, governmental and private agencies launched the Partners in Flight-Aves de las Americas Neotropical Migratory Bird Conservation Program in 1990.

This international effort emphasizes habitat management and protection, professional training and public education throughout North America, the Caribbean and Latin America, to solve the problems facing all birds. Partners in Flight promotes conservation when it should be done -- before species and ecosystems become endangered.

International Migratory Bird Day is Saturday, May 10. International Migratory Bird Day is your chance to celebrate the return of spring and millions of migratory birds to their nesting areas. Whether you're an avid birder or just enjoy watching these winged wonders flit from porch rail to tree, you can be a valuable part of the migratory bird conservation solution. For more information, contact: Partners in Flight, National Fish and Wildlife Foundation, 1120 Connecticut Avenue N.W. Suite 900, Washington, DC 20036.

Amy Salveter is a natural history regional biologist for the Missouri Department of Conservation.