Thursday, March 29, 2007

Supply and demand

Day and night, the sky is alive with life. Migration has begun, and literally millions birds are silently streaming northward in search of nesting grounds.

Only a fraction of these travelers are seen locally, however. They pass by high overhead, often in the middle of the night. Most don’t stop and those that do may pay only brief visits or spend the time sleeping. Sometimes, though, they make forced landings. Countless Fox Sparrows were grounded by the recent nor’easter, showing up in flocks at feeders where they had never been seen before, and generating a flurry of excitement in the bird-watching world – even inspiring some newspaper stories.

All these northbound birds are heading for territory that is barren in winter, but lush with food, both insects and vegetation, in spring and summer. What’s more, the northlands offer virtually unlimited nesting sites – unlike the crowded winter grounds of the South or the tropics.

Thus, migration is nature’s efficient way of handling life’s supply and demand.

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