Some bird species are millions of years old
:D
Jim Williams
Special to the Star Tribune
Published Jul 25, 2002
How old is the oldest living bird? That question is impossible to answer. But, of the few birds banded each year and then recaptured, there is a current champion.
In April, on an island off Wales, a Manx shearwater first banded in 1957 was recaptured. This gull-like seabird was thought at the time of banding to have been hatched in 1952, making it 50 years old. It was preparing to breed when netted on the island this spring.
The oldest wild bird known was a royal albatross that nested in New Zealand. It was at least 53 years old when it went missing. A captive Siberian crane at the International Crane Center in Baraboo, Wis., died in 1988 at the unconfirmed age of 82 years. And many parrots also are long-lived. Experts believe some that are alive today were born in the 19th century.
As for species of birds, some, such as the Eastern bluebird, are known to have existed millions of years ago.
Clues from the past
Fossil evidence, as you might imagine, is rare. Small, delicate creatures like birds are less likely than large animals to leave such remains. A few Eastern bluebird fossils have been discovered. Three leg bones found in an abandoned lime quarry in Florida were the first. They were among other remains of late-Pleistocene animals. A cave in Illinois contained Eastern bluebird fossils dating from 8,000 to 10,000 years ago and caves in Wyoming and New Mexico also have yielded fossils, perhaps as old as 25,000 years.
The best evidence of the age of these birds comes not from old bones, however, but from the DNA of today's bluebirds. Scientists can track the history of a species and its relationship to other species by examining mitochondrial DNA (mtDNA).
This particular DNA is present in large numbers in each cell of a bluebird or any other organism. These strands of DNA vary among organisms, allowing researchers to distinguish one group of organisms from another. It evolves too slowly to be useful in telling one individual organism from another.
In addition, mtDNA is inherited from one's mother, so that any maternally related individuals might be expected to share a similar mtDNA sequence. Thus, study of two species could determine if, at some point in the distant past, two now-distinct species once had what amounts to a common mother.
Studies published in 1997, coauthored by ornithologist Robert Zink of the University of Minnesota, suggest that Eastern bluebirds evolved into a species as long as 2 1/2 million years ago. They split from an ancestor they share with today's Western bluebird, the two being, in effect, sister species.
A geophysical event?
Perhaps this happened when two populations of the common ancestral species were isolated from each other. This division could have been caused by a major geophysical event such as the creation of an inland sea or a mountain range. After the populations were separated, a new species evolved as one of the populations adapted to meet its new living conditions.
Scott Lanyon, director of the Bell Museum of Natural History at the University of Minnesota, is another ornithologist who has worked with mtDNA. One of his specialties is the oriole family. The Baltimore oriole you see in your neighborhood is related to many other oriole species throughout the Western Hemisphere.
A single ancestor
Lanyon and his colleagues, working with oriole DNA samples, have established that all 24 living species of orioles share a single ancestor. Based on the research, he and his teammates are getting close to being able to illustrate -- in shape and colors -- what that oriole looked like.
It is amazing that we can take these trips back in time to determine the beginnings of a species, even to know the appearance of an individual species so far removed. It also highlights what we do not know about our birds -- how to live in harmony with them. We know how to discover their history. We do not yet know how to guarantee their future.
-- Jim Williams is the editor of Minnesota Birding, the newsletter of the Minnesota Ornithologists' Union the state club for people who enjoy wild birds. For information about the organization write to: Minnesota Ornithologists' Union, Bell Museum, 10 Church St. SE., Minneapolis, MN 55455.
