Prehistoric Passenger Pigeons 2

The genesis of my idea that passenger pigeons as Europeans knew them-- Aldo Leopold's "biological storm"-- were a post glacial phenomenon erupting into a new niche came to me as I discussed pre- Columbian America with our little Pigeon Forum-- what Dr. John Burchard calls "pigeons for polymaths".

I bounced some of the details off Tim Gallagher at Cornell in an email. Recently discovered material and info in brackets:

"What effect did the largest population of birds-- large birds at that!-- that ever existed on the continent have on, well, everything? Remember, they "darkened the skies" for days, and nested in dense colonies 65 kilometers long and several wide. Did their droppings have a major effect as fertilizer? [Yes-- first kill, then fertilize]. Did the tree limbs they broke hurt the trees? [Yes, sometimes killing them-- twenty- foot high canebreaks may have grown afterwards in the south ]. Did they spread seeds? Did they wander, or return to the same nest colonies?

What ate them? Are there fewer of it today? Frank Beebe suggests Peregrines and Goshawks in particular. [ I have also found a paper suggesting the now rare eastern burying beetle was affected. Re Peregrines-- if the PP population went up after Columbus, it may have accounted for the Peregrine's former high historical numbers in the eastern forest, an invasion of an uncharacteristic habitat from a bird more associated with seacoasts and cliffs ].

"HOW DID THEY GET STARTED?? Glacial sheets covered their former northern nesting grounds up to 12,000 years ago, and the vegetation in their wintering grounds in the American south and eastern Mexico was significantly different. Were they a southern species that boomed after the glaciers, perhaps helped by a fire- modified ecology introduced by humans?" [ I should add, bolstered by papers sent by Reid and others, that there really wasn't much PP habitat in North America in glacial times-- or in Mexico either. Tundra and tundra- steppe stretched as far south as Maryland- to- be, and boreal forest, with no pigeon food, south of that, while Mexico was wetter with much pinon- juniper where deserts are now ].

I'm not sure that it was just Europeans' effect on the landscape that boosted the pigeon numbers. I suspect North America was and is a sort of work- in- progress and almost inherently in flux, especially since the last glaciation. See Tim Flannery's The Eternal Frontier for more on this subject. And there were other species whose numbers and biomass defy belief-- bison and even more incredibly, grasshoppers-- see Jeffrey Lockwood's Locust .