Cool Facts

• During the summer, the American Tree Sparrow eats nearly 100% animal matter (mostly insects). In the winter it eats none, turning then to eating entirely seeds and other plant foods.
• As in most birds, the American Tree Sparrow is sensitive to changes in day length, which influence the growth of the sex organs. Increasing day length in late winter causes the gonads to grow. This sensitivity to light is independent of vision. Blind tree sparrows in captivity still show normal patterns of gonadal growth when kept in the proper light conditions.
• No one knows just how many American Tree Sparrows exist. But they breed across a vast expanse of northern Canada and Alaska, approximately 100 million hectares (247 million acres). If the area is about 10-20% filled by tree sparrows, and they have 1-ha territories, as is the case near Churchill, Manitoba where they have been well studied, then approximately 10 to 20 million pairs should be breeding.
• A study found that the American Tree Sparrow seems to prefer to look for predators out of its left eye. This preference may be because the right hemisphere of the brain is dominant for processing visual information. Oddly, the Dark-eyed Juncos examined in the same study preferred to look out of their right eyes.