LEAST SANDPIPERS

Those Least Sandpipers amaze me. Actually they're not very flashy birds, especially nowadays wearing their drab, brownish-gray winter plumage. They're only about 4-¾ inch long -- half an inch shorter than a House Sparrow. You can see a small flock at http://www.monterey-bay.net/birds/least_sandpipers.htm.

What amazes me about them is that they nest in a fairly small part of Alaska and Canada's northernmost coastline, yet during the winter they spread over an enormous area, from the southern US and the West Coast all the way to Peru and central Brazil. Moreover, throughout their winter distribution area they're often pretty common. The summer nesting area seems impossibly small for producing so many birds for such a large and densely populated overwintering zone.

I read that Least Sandpipers occur in Mexico from mid-July through May, which is 10-½ months. That doesn't seem to give them much time for nesting. However, in the far north they don't have much time.

Trying to fit together in my mind how all these summer and winter maps, and arrival dates and departure dates relate, I visualize waves of these little birds converging on their northern nesting grounds en masse, creating a veritable local blizzard of Least Sandpipers, then there's a rush to get through nesting and fledging, and finally a rush to leave, maybe as the first snows fall.

Why don't Least Sandpipers breed along the US Gulf Coast, or here, instead of so very far north? I can't see that the stuff they'd peck from tidal basins along the Gulf Coast in summer would be much different from what they get now, here. One thinks in terms of their nesting so far north to escape competition for resources from other birds, but if escaping competition is such a concern then why do such huge numbers concentrate in such a small nesting area?

Who knows why Least Sandpipers are as they are? Maybe the last ice age or a now-extinct competitor is responsible for the species' migratory dynamics, or maybe it all can be boiled down to a mathematical formula showing that their migration strategy is the most energetically efficient for them. Eventually someone will figure it out.