A spotted towhee (Pipilo maculatus) has been residing in Rye, New Hampshire during the cold and snowy winter of 2013/2014. This is quite rare considering that the normal range for the spotted towhee is located entirely west of the Mississippi River. The bird has been the subject of a local pilgrimage of bird watchers as they attempt to add this species to their list of bird species they have personally seen, called a life list in the bird watching community vernacular.
The spotted towhee, according to the "iBird Explorer Pro 2" app by Mitch Waite, normally spends its winters in a territory bounded on the north by British Columbia, Canada, and south into Baja California and central Mexico. They can be found from the Pacific coast to Oklahoma and south-central Texas. In the spring and summer breeding season, they may extend out through Montana and the Dakotas. At no time of the year, however, would one expect to find a spotted towhee in New Hampshire or anywhere even close to the northeast United States.
How, then, does a bird end up all alone more than a thousand miles away from its normal territory? We think of birds as having an unerring direction sense as typified by the use of pigeons to carry messages across long distances to very specific locations. For the most part, that's true. Birds use a variety of methods to determine direction when they migrate.
They may orient by the position of the sun, moon and stars or by detecting the Earth's magnetic field through a system that is still poorly understood. For many birds, it can be as simple as following the rest of the flock trusting that they have been there before and know where they're going.
Many first-year birds, say researchers Bingman, Jechura and Kahn of Bowling Green State University in their paper "Behavioral and Neural Mechanisms of Homing and Migration in Birds", end up flying alone at night, because they have not yet established themselves as part of the greater social community. As Bingman, Jechura and Kahn note, while young birds must be exposed to the night sky during their first year in order to learn to use it as a navigation reference, indicating that part of their guidance system is therefore learned, other parts of their navigation ability seems to be hard-wired into their genetic code. Birds in North America will typically orient themselves to fly away from the rotational axis of the night sky even when an artificial sky and rotation point is provided under experimental conditions. In the wild, that equates to flying south for the winter. If, however, a bird is born with internal "wiring" that is a bit different (whether due to a minor mutation or some other reason), and it hasn't yet assimilated into a flock that it can follow, its internal direction sense may tell it to fly toward the rotational axis or parallel to it. In some cases, this could be a fatal flaw that puts the bird in a winter environment that it isn't equipped to survive. In the case of the spotted towhee that is currently wintering in Rye, New Hampshire, the winter has been unusually cold and snowy, but concerned birders have been sprinkling the ground with bird seed to help it find enough calories to survive. This strategy seems to have helped as the bird has, thus far, made it through the winter in seemingly good health. Assuming that it makes its way back to its normal summer territory this spring, it is possible that its internal preference for a west to east winter migration may be over-ridden by the social cues of its fellows flocking up to fly south, but who can say, perhaps its internal guidance system error is a dominant genetic trait and its descendants will end up spending a year wintering on the New Hampshire seacoast as well.