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Orioles on the Wintering Grounds: Life in Costa Rica


Winter in Central America
Imagine spending every summer in Canada and every winter in Costa Rica! Birds that move between North America and Central or South America are called neotropical migrants. Traveling back and forth between two completely different environments every year is how orioles and many other neotropical migratory birds spend their lives. Why do they make such long journeys? Alexander Skutch was someone who wondered.


Life in the Tropics
Alexander Skutch was one of the most famous ornithologists in the world. He migrated from the United States to Costa Rica and stayed there. He devotes his life to studying tropical birds and their world, and writing books to share his knowledge. He wrote in Life Histories of North American Blackbirds, Orioles, Tanagers, and Allies about the Baltimore Oriole: "During the northern winter, it resides throughout the region from Guatemala to the Isthmus of Panama, on both the Caribbean and Pacific coasts and high up into the mountains. Scarcely any other winter visitant is so widely and uniformly distributed throughout the area.. In "the arid coast of El Salvador... I found these orioles abundant among cacti and low thorny trees... In Honduras and Guatemala...the Baltimore orioles pass the winter in large numbers, amid lofty rain-forests, lush thickets, and extensive banana plantations." Dr. Skutch even "found a few Baltimore orioles which had apparently settled down for the winter among the oaks, pines, and alders on the Sierra de Tecpan in Guatemala, at an altitude of 8,500 feet above sea level, where at this season night were penetratingly cold, and every clear dawn revealed all the open spaces white with frost." What an adaptable bird! No wonder a handful can survive at feeders during winter in the United States.


The Buddy System
Dr. Skutch said, "During the winter months, the Baltimore orioles roam about singly or in small groups of two, three, or four, more often than in larger groups. Although a dozen or so may at times be seen feasting together in some especially attractive flowering or fruiting tree, or share the same roost, the birds are only slightly gregarious during this season and form no big, closely knit flocks like those of wintering dickcissels and cedar waxwings. Adult males pass the winter in brightest orange-and-black plumage, and are excelled in beauty by few even of the most brilliant of the native birds; but females and young males predominate."


Shout from the Highest Treetops

Listen to the Oriole's Call Note
Wait for download; 97 K file.
Recording Courtesy of Lang Elliott

Listen to the Oriole's Song
Wait for download; 58 K file.
Recording Courtesy of Lang Elliott

Dr. Skutch said Baltimore orioles sometimes sing their full song when they arrive in Costa Rica in autumn, and again before they fly north again in spring, but "a sharp churr (its call note) is the oriole's most frequent utterance while in its winter home."


Coast of Riches
Costa Rica is a tiny country--it is no larger than the state of West Virginia. Yet it is known to be one of the most biologically diverse places on earth with over 300 species of reptiles and amphibians, 200 species of mammals, thousands of species of plants, and more than 800 species of birds--more different kinds of birds in this little area than in all of the continental U.S. and Canada combined!

How can such a tiny country have so many kinds of living things? Scientists believe it is partly due to the fact that Costa Rica (and Panama) lie right in between North and South America. Being this close to both continents made Costa Rica something like a bridge which plants and animals could migrate across over the centuries.

Also, the very name "Costa Rica" gives us another clue. It means "Coast of Riches." Costa Rica lies between two oceans, and its land lies at elevations from zero to over 10,000 feet above sea level! The result of this is that Costa Rica has been left with one of the most diverse collections of plant life anywhere on the planet--and as a result, the neotropical migrants have one of the most diverse food sources on earth!

This richness means there are many things for orioles to feed on. Baltimore Orioles are believed to feed on the following while in Costa Rica: nectar from trees (Erythrina, Inga, and Calliandra), vines, and many different types of epiphytes (plants that grow on other plants, such as orchids); they also eat bananas and other fruits, as well as the insects found on branches and leaves.

Biodiversity and the Seasons
Close your eyes and imagine the dead of winter in the north. Feel the cold, picture the darkness, and listen to the silence. Now fill you mind with thoughts of spring-- birds singing, frogs calling, flowers blooming and sunshine greeting you in the morning. When you contrast the number of bird species in your region during winter with the number in summer, the results can be impressive. The arrival of migratory songbirds increases the species richness of the region. Scientists believe that the stability of ecosystems depends on the rich interaction between species, and that these natural systems sustain all life-- including our own!


Try This! Journaling Question

With such a rich variety of food on the wintering grounds, why so orioles and other neotropical migratory birds leave and undergo all the hazards of migration to come to North America?

Try This! Investigation
How does avian biodiversity (variety in bird species) change with the season in your part of the world?

  1. Look at a field guide to birds of North America. Using the range maps in the guide, count the number of bird species that are found in your region in the winter months.
  2. Now count the number of species in your region during the breeding season.
  3. How does the avian biodiversity of your region change with the seasons?

 

 
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