Monday, January 11, 2010

Lovers in the snow

The UnterWarnow is frozen, and snow is building up on the ice. Sunset will come 7 hours and 45 minutes after sunrise today. The crows and blackbirds are digging in the snow looking for food, and the birds that usually haunt the harbor all winter are gone, perhaps to the south, perhaps out to the Baltic where the water isn’t solid.

But in the tree in front of my office window, two magpies are carrying fresh twigs into a crook between three branches. There is only one reason I know of why they would be doing this: they are building a nest. Most birds, including magpies, only build nests to lay eggs in, and now is not the time to lay eggs. It is too cold for the eggs to develop (even with mom sitting on them), and if they did hatch , there would be nothing to feed them. Any nest built now isn’t even likely to still be in good enough shape to use come spring. The spot where they are putting the twigs is near the top of the tree, on the branch closest to the river, and shakes whenever the wind blows, which it does frequently.

This raises the question of why? When other birds in the neighborhood are struggling just to keep from freezing or starving, why are the magpies wasting their time and exposing themselves to the cold building a nest they can’t use? Perhaps the cold has driven them mad? Maybe they are pulling food out of the dumpster of the near by grocery store, and having plenty of food, think it is time to breed? A genetic disorder?

There may be some perfectly good reason for this (pair-bonding activity?) but I’m not sure I buy that.

When my colleagues and I were writing a paper on the definition of behavior, many of previously published definitions we came across specified that behavior is adaptive, that it will tend to increase the fitness of the individual performing the behavior. We omitted this from our definition, because there are so many behaviors whose adaptive significance is uncertain, or which seem maladaptive. It is certainly true that most behaviors are adaptive, some, like building a nest in a snow storm, probably are not.

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