Smithsonian Institution; it is believed that this species once constituted 25 to 40 per cent of the total bird population of the United States. It is estimated that there were 3 billion to 5 billion passenger pigeons at the time Europeans discovered America.
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"Ask". Diarsipkan dari versi asli tanggal 2007-09-11. Diakses tanggal 2007-11-17.
