From the big questions (how many species of birds are there?) to specifics (should the Bullock’s Oriole and the Baltimore Oriole be merged into one species called the Northern Oriole?), birders have long endured a bit of confusion. It seems even the most eminent ornithologists disagree on these and similar conundrums.
In 1946, a paper published by Ernst Mayr asserted that there were 8,616 species of bird worldwide. Today, the consensus is that there are closer to 10,000 although estimates vary widely. What happened?
In 1973, scientists decided that the two most common American orioles, the Bullock’s Oriole in the west and the Baltimore Oriole in the east, were really the same bird. Where their ranges overlapped, they mated and produced fertile young. Then, in 1995, the two species were separated again! Why?