When the last of five types of endemic Moho and Chaetoptila birds disappeared some 20 years ago, the world lost more than just five rare Hawaiian songbird species.

According to a 2008 study conducted by scientists at the Smithsonian Institution and published in the Dec. 11 edition of the international science journal Current Biology, the five now-extinct birds were part of a distinct family of birds previously unidentified.

The Hawaiian birds, known as oo and kioea, were long assumed to be related to honeyeaters, which exist in Australia and its surrounding islands.

First recorded during Capt. James Cook’s third voyage to Hawaii in 1779, the oo and kioea were classified as part of the family Meliphagidae due to strong similarities in appearance and behavior to the honeyeaters.

However, an assessment of molecular data undertaken by Robert Fleischer, a molecular geneticist at Smithsonian’s National Zoo and National Museum of Natural History, and Storrs Olson and Helen James, curators of birds at the National Museum of Natural History, revealed that the Hawaiian and Australasian birds are not related at all and that the oo and kioea represented a unique and separate family.

"The similarities between these two groups of nectar-feeding birds in bill and tongue structure, plumage and behavior result not from relatedness, but from the process of convergent evolution — the evolution of similar traits in distantly related taxa because of common selective pressures," said Fleischer, lead author of the study. ("Taxa" refers to groups or populations.)

The scientists used DNA sequences from museum specimens of Moho and Chaetoptila that had been collected in the 1800s. They determined that while the two genuses of Hawaiian birds shared a common ancestor, they did not share the same evolutionary path as the honeyeaters.

According to the scientists, birds of the genus Moho and genus Chaetoptila were divergent members of a group of songbirds that includes waxwings, neotropical silky flycatchers and palm chats, which the scientists now designated as a new family, the Mohoidae.

It is not known what caused the Mohoidae birds to become extinct, although it is assumed that disease, human development and introduced species such as mosquitoes, mongooses and rats likely contributed.