Herds of Birds
February 14, 2025
Wintering birds could warm up by foraging in direct sunlight. However, research shows that mixed-species flocks of wintering sparrows chose to avoid predators and forage in the shade, even in cold weather when sunlight would offer warmth.
Researchers found that foraging in sunlight makes birds easier targets for predators. It also hinders their ability to see attacks because of the sun's glare.
The study took place in Terre Haute, Indiana, on a 4-by-6-foot concrete pad covered with finely ground cornmeal. Vertical shade boards split the foraging area into 10-inch strips of sunlight and 7-inch strips of shade.
Over winter, researchers conducted 18 one-hour observations on days with clear sunlit and shaded strips. They also did 13 hour-long observations on cloudy days when shadows were not visible. Most of the observed birds were Dark-eyed Juncos, with American Tree Sparrows making up the next largest group. A few Northern Cardinals, Song Sparrows, White-throated Sparrows, Swamp Sparrows, and Field Sparrows were also observed.
Since 40% of the research pad was shaded, around that percentage of birds would typically be found in shaded areas without a preference. However, 75% or more were usually seen in the shade.
