For example, the Baltimore Oriole is not a species any more. About twenty years ago scientists decided it was the same bird as the Bullock's Oriole. The Baltimore Oriole lives in the Eastern United States and the Bullock's Oriole lives in the Western United States. Both birds are now called the Northern Oriole. Of course, just the opposite can happen.
Scientists can change their minds after more evidence is produced.
There seems to be a trend today toward splitting birds. This is because better methods of research are now available to examine birds at the microscopic level. Today there are many scientists investigating birds. They work at places like The Academy of Natural Sciences in Philadelphia or Cornell Laboratory of Ornithology or Pennsylvania State University or Louisiana State University. It is certain that their work will make bird species appear and disappear as they continue lumping and splitting.