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Songbirds Arrive on the Yucatan Peninsula
December 5, 1997
"Ya llegaron! Acabo de regresar del manglar donde he ido cada manana y he
visto una gran cantidad de nuevas aves que han llegado recientemente.
Estan muy cansadas y tienen mucho hambre por su viaje tan largo." dice Maro
"They're here! I just got back from the mangrove swamp where I've gone each
morning and spotted a host of new species that has recently arrived. They're worn
out and hungry after their long trip," reported, Mauro Berlanga research biologist
with ProNatura Yucatan in Mexico.
Huge numbers of birds have just moved into Mexico, Central and South America, and
Caribbean. Scientists estimate that a grand total of 2 to 5 million individual birds
take part in this biannual migration. Species which breed west of the Rocky Mountains
spend the winter in northern and western Mexico. Some eastern species travel to the
islands of the West Indies and the Caribbean. A few migratory birds fly straight
to South America without stopping. The rest, or approximately one-third of the total,
migrate to the Yucatan Peninsula, the southern Mexican state of Chiapus and the Peten
region of Guatemala. Why do you think such a large percentage of the total number
of migratory birds go to the Yucatan?
A quick look at a map of the Western Hemisphere should reveal a clue to this question.
Migration is hard work. Itís no wonder that birds which fly over the Gulf of Mexico
seek out the closest possible destination to land. While it is not an airport, the
north coast of the Yucatan Peninsula does serve as one large arrival terminal for
huge numbers of birds moving over the Gulf each autumn.
Energy to Burn
Birds migrating over land from eastern and central regions of Canada and the U.S.
to southern Mexico will eventually hit a big hurdle, the Gulf of Mexico. The Gulf
covers over 1,000 square km. and has only a few scattered, tiny islands. Upon reaching
the Gulf, birds must decide whether to fly around the Gulf, stopping at wood lots
along the way, or fly straight over it. For years, ornithologists wondered if those
birds which flew over the Gulf made the trip in a non-stop flight.
Recently, scientists have used radar systems to detect waves of thousands of birds
flying over the Gulf of Mexico. Radar images now confirm that bird migration over
the Gulf is indeed a non-stop flight and that the flight takes a total of approximately
20-40 hours depending on the weather. Can you imagine staying in the air for nearly
two full days? How do the tiny birds, some weighing less than one ounce, stay airborne
for this long to make this extraordinary trip?
Energy to fuel migration is stored in little lumps of yellow fat which are found
underneath the skin of the bird, on its back, throat, and sides. Fat supplies a lot
of energy and it is also very dense. A few grams of fat can be enough to fuel a hummingbird
or a warbler for a thousand miles over the Gulf and beyond.
The list of migratory bird species which arrive at the Yucatan Peninsula each year
includes a staggering 189 species. This does not include resident species, birds
which live on the Yucatan all year around. All told, close to 500 migratory and resident
species make their home on the Peninsula. The northern coastal region of the Yucatan
Peninsula includes many wetland areas which provide rich food supplies for hungry
migrants. As birds move southward and inland on the Peninsula, they find scattered
forests and open areas providing diverse habitat in which to spread out and establish
Some species spend the entire winter on the Yucatan Peninsula while others move southward
toward the states of Chiapus and Wahaka in southern Mexico and the Peten region of
northern Guatemala. Southern Mexico is extremely important to birds and supports
even greater numbers of migratory and resident birds than the Yucatan Peninsula--upwards
of 800 species. Just like areas of the U.S. and Canada that attract many different
nationalities of peoples, Southern Mexico is at a confluence of migratory pathways.
The region is a melting pot for migrants coming to Mexico from western regions of
North America, those flying over the Gulf through the Yucatan Peninsula, as well
as those traveling from the east following the Texas coast into Mexico.