Wednesday, October 6, 2010

‘Birds don’t fly South for the Winter’

Birds of Ambergris Caye
“Birds can fly where they want to, when they want to, or so it seems to us,”
‘Birds don’t fly South for the Winter’
It’s September, and from now until late April Bubba and I will be enjoying an unusual variety of migratory
Avifauna visiting Ambergris Caye and its Bacalar Chico Reserve. The northern part of the planet has begun
to lean away from the sun. Invisible plotable lines of temperature gradients called ‘isotherms’ move further
south on the weather maps and all life on earth pays them heed.
The Bacalar Chico Reserve on the north end of Ambergris is a 60 square mile terrestrial reserve and
serves as a refuge for migratory birds. About 225 species of long distance migrants occur in Mexico and
Northern Central America. Observers have long theorized that migrants use mountain ranges, rivers, and
coastlines for guidance. Scientific research suggests that some birds may also set their courses by the sun, by
the patterns of stars, even by the lines of force in the Earth’s magnetic field, perhaps in combination with
gravity. Scientists don’t know exactly how the migrating birds find their way over long distances, but they are
discovering that birds tune into an astonishing variety of sensory cues that may be used for navigation.
Bubba believes Birds use specific migratory paths that consist of rivers, lakes, and various other food
sources like a dotted line of rest stops. These paths are called flyways. The Atlantic flyway leads migratory
birds from as far north as Greenland down Florida’s eastern coast across the Caribbean into Cuba, Haiti,
and Dominica.
The Mississippi flyway leads birds from Alaska and middle Canada down the Mississippi River Valley
to the Gulf of Mexico where it divides, leading some to Cuba and some to the Yucatan.
It is the Central and Pacific flyways that lead the majority of migratory birds to Ambergris Caye. The
bottleneck effect of the flyways narrowing at the base of the Yucatan cause a concentration of migratory
Avifauna looking for shelter, food, and water. The Bacalar Chico Reserve seems to be a logical place to stop
for this, and creates a birdwatching spot second to none.
I said to my resident expert, “Birds in the North use this cooling as a signal to begin their annual
migration southward. Bubba gave me a look that made me feel I had said something wrong. With a little
bit of an annoyed tone he said, “birds don’t fly south for the winter, Canadians do. The birds fly North for
the summer and I bet you think that’s the same thing!”
“Yes, and the way I look at it that’s called ‘the same difference.”
Bubba sighed and said,” If you look at this properly, you’ll discover something you didn’t know about
migration. Birds we see in Belize, (Neotropicals) have been moving north slowly each season and retreating
a little less south since the end of the ice age.
The American continent was very different during this frozen era. Most living things where compacted
into areas near the equator.
The ancestors of neotropical migrants originated in Amazonia (an area believed to be 15 million years
old, known today as Brazil). Areas north of this were not at that time in the earth’s history temperate
enough to reside in. Amazionia was then and today the greatest expression of life on the planet. One third
of the world’s birds still live there. As the ice age ended, areas to the north of Amazonia were habitable
during summer months and provided refuge from competition for food and shelter in this over-populated
area. But in winter months migrants were forced to retreat. Each year as the ice receded, more northern
territory became available as refuge during summer months and migration distances increased. As some
found the decreasing winter months tolerable they became residents in places like Belize. Canadians go
home in spring and birds migrate north. Does that seem like a ‘same difference’ still? I said you where
going to learn something new.”
San Pedro tour operators are now offering day trips into the Bacalar Chico area September also marks
the beginning of the slow season for tourism this might be just the time for Bubba and I to explore the
Island we are living on.