(Rhiannon Crain, February 9, 2017)
In the spring and summer, when bugs are buzzing and plants are blooming, a bird’s diet will most likely consist of a variety of abundant, protein-rich insects. In northern regions where warm seasons change to cold, those insects become fewer and harder to find, convincing many avian species to migrate to tropical locations where insects are found year-round, or to change-up their primary food source–relying not on insects, but on winter berries. Read on to learn about putting this valuable habitat feature to work.
Migratory neotropical songbirds are usually insectivorous and are among many who make the long journey between North and South America to feed almost exclusively on insects and other invertebrates, like worms. Many warblers, like the Common Yellow-throat shown above, will migrate to North America during breeding season to take advantage of the abundant insect foods that appear in the spring and summer and return south as those food sources dwindle. They almost never eat food from plants, which is one reason you won’t see them at your feeders.
On the other hand, many songbirds are year-round residents and will stay in northern latitudes even during the coldest winter months. They are able to eat a larger diversity of foods as the seasons change, including berries, seeds, and nuts, that are available from native shrubs and trees. The image above, taken in November, shows an American Robin in Ontario, Canada investigating some Mountain-Ash berries, still lingering from when they ripened in early autumn. Year-round residents rely on persistent berries, like these, to sustain them through the winter season.
In the spring and summer, this same robin will be found gorging on insects, like caterpillars in the image above, as soon as this food source becomes available. Research has even suggested that these seasonal shifts in food abundance help cue physiological changes that prepare birds for breeding season. A landscape with berry-producing native trees and shrubs provides the resources that support these seasonal cues by producing high-fat berries in the fall and attracting insect food in the spring.