I have always heard that passenger pigeons were killed off by hunters.
But a colleague claims that they really died out because of deforestation. Their habitat, the great deciduous forests of the Northeast, were clear cut in the 1800s and then later replanted with quicker-growing evergreens.
So what’s the straight dope?
Both factors probably played a role. However, hunting unquestionably had a major impact. Enormous numbers were killed and salted in barrels at their breeding colonies to be sold in eastern markets. The pigeons largely fed on nuts, including acorns, beechnuts and chestnuts. Destruction of the midwestern forests deprived them of some of their food sources. However, it was the breakup of their breeding colonies that probably had the most devastating effect. Passenger Pigeons seemed to need the stimulus of many other nearby pairs in order to breed; once they were reduced to a few scattered colonies they rapidly disappeared.
I agree with Colibri (and I’m getting a stamp made to that effect as this seems to be my mantra). Deforestation and massive hunting most likely reduced populations to levels where their colonial reproductive lifestyle was ineffective. Several captive breeding attempts were not successful most likely due to insufficient stock numbers. Perhaps high numbers were required to stimulate hormonal levels to some threshold level, resulting in reduced egg production (deadly when you only produce 1 or 2 eggs) or appropriate behaviors.
Gruesome factoid - you can still see passenger pigeons. The Field Museum in Chicago has some stuffed specimens on display.
Gives me the shivers when I see 'em. Very sad.