14 DAY TRIAL // Scientists studying bird's migration discovered that, after the Panama “land bridge” formed, birds from the North of the American continent migrated South and colonized the existing tropical species.
The two American continents were separated until 3 million years ago, when a tectonic uplift took place in Central America. A land corridor formed in today's Panama and it allowed species to migrate from one side to another.
Research revealed several bizarre aspects about ancient birds. One of them is that even if they had the ability to fly, before the land bridge, no specimens tried to cross the waters and get to the other continent. The tectonic uplift allowed thus not only mammals that could not fly to pass to the other side, but birds as well. This crossing over allowed one of the biggest exchange between species, isolated for millions of years.
Genetic data from 11 orders, 34 families and over 100 genera was analyzed and scientists came up with yet another very interesting observation. Most of the Northern bird species repeatedly invaded the South, still Southern birds remained close to the tropics.
Lead author of the study, Brian Tilston Smith from the University of Nevada said that “this inter-continental migration was far from even. While within the tropics around the equator exchange was equal in both directions, between the temperate zones of North and South America it was not. Avian lineages from the northern Nearctic regions have repeatedly invaded the tropics and radiated throughout South America. In contrast species with South American tropical origins remain largely restricted to the confines of the tropical regions.”
Several studies showed that 50 percent of mammals living on the South continent have Northern origins while only 10 percent of the Northern species had origins in the South. Scientists are convinced that the figures are almost the same for birds.
“Our study suggests the formation of the Panama land bridge was crucial for allowing cross continental bird migration. We believe that the ability of species to colonize and radiate across this area represents an important and under appreciated factor to the distribution of species around the equator” finally added Smith.