Avian diets are inherently linked to the botanical world, relying on diverse plant resources that change dramatically with the seasons. This seasonal variation dictates the movements and behaviors of birds throughout the year. The type of plant material consumed varies widely, from energy-dense dry grains to sugary liquids, depending on the species’ specialized anatomy and nutritional needs. Understanding which parts of plants birds consume offers insight into how to best support local and migratory populations.
Plants Cultivated for Seeds
Seeds are a foundational food source, particularly for many common backyard birds that possess strong, conical bills adapted for cracking hard casings. The familiar sunflower is a prime example, with its two main types offering distinct benefits. Black oil sunflower seeds are favored by many species, including finches, chickadees, and cardinals, because their thin shells are easily cracked and the kernels have a high fat content. Striped sunflower seeds have a thicker shell that requires more effort to open, often deterring smaller or weaker-billed birds.
Beyond the large, obvious seeds, finer grains are consumed from plants such as millet and safflower. Pearl millet, a fast-growing grass, offers generous seed clusters that are highly attractive to ground-feeding birds like doves and quail. Safflower seeds are particularly noted for attracting cardinals and house finches while being less appealing to squirrels and certain unwanted bird species.
Shrubs and Trees Bearing Fruit
Fleshy fruits and berries from shrubs and trees are an important part of the avian diet, particularly for species that migrate or require quick, high-energy meals. These plants are often categorized by whether their fruit is quickly consumed or designed to persist into the colder months. Soft, sugary berries, such as those from serviceberry and elderberry, are high in carbohydrates and are typically eaten immediately upon ripening in the summer by robins and waxwings.
The fruit of plants like dogwood and viburnum are often rich in fats, making them an ideal fuel source for migrating songbirds preparing for long journeys. Other fruits, such as the pomes of hawthorn and the berries of winterberry holly, are generally harder and less palatable when first ripe.
These persistent fruits remain on the branches through fall and into winter, offering a crucial food source when other options are scarce. The berries of sumac and holly, for instance, may be ignored in favor of sweeter alternatives until the deep winter, when they become a reliable meal for species like cedar waxwings and mockingbirds.
Specialized Plant-Based Resources
Birds also utilize specialized plant components beyond the readily available seeds and fruits, often requiring specific anatomical adaptations to access. Nectar is a high-sugar liquid consumed primarily by hummingbirds, who use their long, specialized tongues to reach deep inside tubular flowers. Plants like trumpet honeysuckle and red buckeye produce these red or orange flowers, which signal a rich sugar source to the birds.
Tree sap is another specialized resource, accessed most notably by the yellow-bellied sapsucker, a type of woodpecker. These birds drill small, shallow holes, known as sap wells, into the bark of trees like birch, maple, and American beech to drink the sugary fluid that pools there. The high sugar concentration of the sap offers a reliable energy source, especially during early spring.
When other food is unavailable during winter, some birds turn to less-digestible plant structures like buds and catkins. Species such as ruffed grouse and specific finches, like the pine grosbeak, rely on the buds of trees like aspen and birch to survive the cold.