Mexico’s importance for trans-continental migrations of birds of prey

By virtue of its geography, the Gulf coast state of Veracruz is one of the best places in the world to see the annual migration of birds of prey (raptors) from North America to Central and South America.

Between 4 and 6 million birds (eagles, hawks, vultures, falcons, and kites) make this trip each way each year to trade the harsh winter and scarce food in one hemisphere for better conditions in the other hemisphere. The migration south takes place September-November, and the return migration passes overhead in March-April.

Since most raptors are relatively large birds, and they are accompanied by other species such as storks, white pelicans and anhingas, this annual migration is one of the most awesome birding spectacles anywhere in the world. Each passing flock contains tens of thousands, in some cases hundreds of thousands, of individuals.

The raptors fly during daylight and rest overnight. Their New World songbird cousins, who also migrate in vast numbers, prefer to feed and rest during the day and then fly at night. Most songbirds take a direct migration route from the eastern USA to Central and South America, flying directly over the Gulf of Mexico in a “single, epic 18-hour flight”. Raptors, on the other hand, prefer a more leisurely approach, leap-frogging along the coastal plain.

Why do they fly through Veracruz?

The main reasons are:

1. Relief: Mexico’s mountain ranges, especially the Sierra Madre Oriental {Eastern Sierra Madre) and Volcanic Axis, funnel the birds towards the east coast, but the Gulf of Mexico provides a natural barrier preventing the birds from attempting routes further to the east. At its narrowest, this funnel is only 25 km (15 miles) wide.

2. Climate: The wide coastal plain warms up sufficiently to provide ascending thermal “bubbles” which help keep these large birds aloft and minimize  the energy expenditure required to soar and fly large distances. Raptors use the thermals to soar to about 1000 meters (3000 feet) above the ground, before gliding in their desired direction of travel gradually losing height until they pick up another thermal at a height of about 300 meters (1000 feet), repeating the process as often as needed. On a good day, they will cover more than 320 km (200 miles) in this fashion before resting for the night.

3. Biogeography: The varied landscape, vegetation and animal life in habitats ranging from tropical wetlands to temperature forests, offers plenty of potential food sources for the raptors.

This massive migration has been studied since the early 1990s and scientists continue to tag birds today in order to update their estimates of bird populations and of the precise timing and routes involved. An official counts is held each year from 20 August to 20 November, organized by Pronatura Veracruz. The count is held in two locations: Cardel and Chichicaxtle (see map).

The counts have confirmed that Veracruz hosts the most concentrated raptor migration in the world.

One of the major long-term threats to this migration is habitat change in central Veracruz. Pronatura Veracruz sponsors an environmental education program known as “Rivers of Raptors” which tries to address this issue, helping local landowners appreciate the need for watershed protection and for an end to deforestation.

Pronatura’s work with raptors and the local communities is partially funded by ecotourism, and hawk-watching has become an important component of Mexico’s fledgling “ornithological tourism” market. Other key sites in Mexico for birding tourism include the tropical forests of the Yucatán Peninsula and Chiapas, and the San Blas wetlands in the western state of Nayarit.

In fact, Mexico is one of the world’s most important countries for birds, home to 1054 species of birds, 98 of them endemic, including 55 globally threatened species. Mexico has no fewer than 145 recognized “Important Bird Areas” (IBAs) of global significance, which between them cover 12% of the national land area (see summary map below).

• List, description and discussion relating to Mexico’s 145 IBAs [pdf file – English]
• List, description and discussion relating to Mexico’s 145 IBAs [pdf file – Spanish]

Want to read more about the raptors?

• River of Raptors, by Susan McGrath (Audubon magazine)

Related posts:

• Mexico’s mega-biodiversity
• The diversity of species (plants and animals) in Mexico
• Which areas of Mexico have the greatest biodiversity?
• Mexico’s top 13 natural wonders
• Mexico has forty UNESCO-designated biosphere reserves
• The thorny issues of plant and animal trafficking and biopiracy in Mexico