The extinct passenger pigeon now occupies a better understood place within the family tree of pigeons and doves. Scientists from the Illinois Natural History Survey at the University of Illinois used DNA extracted from museum specimens to analyze the passenger pigeon's genetic makeup. By comparing the DNA of the extinct pigeons to that of living pigeons and doves, the researchers were able to determine the passenger pigeon's closest living relatives. It was previously thought that passenger pigeons were related most closely to mourning doves. But the recent analysis showed that passenger pigeons were instead closer relatives to the band-tailed pigeon, a species that inhabits western mountainous regions of North and South America. In the early 1800s, passenger pigeons were among the planet's most abundant bird species. Their range once stretched over the eastern and central forests of North America . Passenger pigeons formed vast, dense flocks that consisted of millions of birds. During the mid to late 1800s, habitat destruction and intense hunting drove the birds to extinction. The last passenger pigeon died at the Cincinnati Zoo in 1914.