Naturespeak A naturalist's view of the world

January 16, 2009

Sparrow Does the Chicken

Filed under: Uncategorized — wykes @ 11:11 pm

White-throated Sparrows take winter very seriously but there’s something about their demeanor that takes the edge off the season for the rest of us. All active winter wildlife (the dead ones don’t count) are engaged in a daily struggle for survival.  The search for food and shelter can be an all-consuming effort when things get tough. White-throats are always searching about, foraging, calling, or gathering into small rambunctious feeding flocks. In short, they are constantly reminding us just of how hardscrabble their tiny lives can be. They do it with such grace and dignity, however, that they make it look natural.

Although they offer some pretty fascinating  patterns, most sparrows are relatively plain brown birds. White-throated Sparrows stand out among the sparrow set because of  their striking black, white, and yellow crown markings. Being good looking is a definite eye-catching trait for bird and man alike (not this particular man, mind you). A key characteristic, and one which probably goes without saying,  is their white throat set against a buffy gray breast (see above). Hardly anything in nature is as it first appears, which is why I’d like to get back to these markings in a moment. First, we need to take a look at how these sparrows forage.

White-throats spend a large part of their time on or near the ground. They are ground gleaners, which means they specialize in  finding hidden foodstuff on the ground. Their discovery technique involves scratching about much like tiny barnyard chickens. By hopping forward with both feet and then briskly pulling them back, leaves and snow cover are sent flying and a space is cleared to reveal what lies beneath. During the winter they expect to reveal enough seeds or hibernating insects to keep them going.  Take a look at this short video I made of one of these birds actively burrowing into some bark chips (watch movie here). It was an especially cold day and the promise of a sheltered patch of uncovered ground was too much for it to ignore. This fact also explains why his feathers are fully puffed out as a buffer against the single digit temps.

Burrowing is the only word to describe what these little guys can do. Given the proper incentive (that being food) they can dig an inch or more into the ground. A determined individual will dig a series of small potholes over a large area if the rewards are sufficient to reward the labor. It is a deliberate act on their part to nearly deplete a spot before moving to another. They are not normally social birds, but during the winter small flocks of feeding White-throated Sparrows will gather together for mutual safety. Large groups can afford to be further from cover, so the benefit is clear. There is a definite hierarchy within these impromptu groupings. I guess you could call these ground rules to insure that there is enough to go around. Dominant birds, for instance, are allowed  to pick areas closer to cover than younger subordinate birds. It is a matter of natural fact that the more exposed birds – i.e. the yearlings – will get picked off more frequently by predators, but these things are probably not brought up at the team meetings.

There is one more subtle mark of rank within a White-throated Sparrow society group. These sparrows come in two different genetic “morphs” that exist side by side – distinguished by the intensity of their colors. Until about thirty years ago, these color variations were considered differences between adult and juvenile traits, but such turned out not to be the case. The so-called “tan striped” individuals have muted colors and off-white crown stripes. The individual in the above picture, and the one in the video, are examples of this type of  dull bird. “White-striped” birds, like the one shown here, are brightly marked with bleach-white striping and bright yellow spots above the eyes.

Being known as a dull bird might seem like a downer but it has some advantages. It’s easier to hide from those nasty predators without that flashy white head pattern. Oddly enough, the opposite morphs are attracted to each other. Not every sparrow in this clan is on equal footing with the next. It is almost an avian case of reverse discrimination or something. Male tan-stripes prefer the romantic company of  female white-stripes and vice versa.

Admittedly, these affairs of the heart and morph don’t really matter in the dead of winter. The birds will have plenty of time to act out their romantic inclinations when they return to the boreal forests for the nesting season. The important thing now is to get through the winter without getting dead and to scratch your way to Springtime.

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