Many birds are omnivores, eating a mix of plant and animal foods, but not all of them. Birds as a group span every dietary category: some are strict carnivores (like hawks and owls), some are specialized herbivores (like geese), and a large number fall somewhere in between. The omnivores, those that regularly eat both plant and animal matter, include some of the most familiar backyard species: crows, robins, chickadees, starlings, and sparrows.
What Makes a Bird an Omnivore
Omnivory in birds means getting nutrition from both plant and animal sources. In practice, most avian omnivores lean heavily toward one side. They’re better described as seed-eaters or fruit-eaters that supplement their diet with protein-rich insects, rather than species that split their meals evenly between plants and animals. The American Crow is a good example: one study found its diet breaks down to roughly 72 percent plant matter (seeds, fruits, grains) and 28 percent animal matter (insects, worms, small vertebrates, eggs).
Ornithologists distinguish between two types. Obligate omnivores genuinely need both plant and animal foods to meet their nutritional requirements. If deprived of either source, they develop nutrient deficiencies. Facultative omnivores can technically survive on their primary diet alone but eat a broader range of foods when the opportunity arises. This distinction matters because it means “omnivore” covers a wide spectrum, from birds that absolutely must eat insects alongside their seeds to birds that simply grab a caterpillar when one crawls past.
Common Omnivorous Bird Families
Corvids (crows, ravens, jays, magpies) are perhaps the most visibly omnivorous birds. They eat fruit, seeds, nuts, insects, small mammals, eggs, carrion, and human food waste. Their intelligence and adaptability go hand in hand with this dietary flexibility.
Thrushes (robins, bluebirds, hermit thrushes) mix earthworms and insects with berries and fruit. Chickadees and titmice eat seeds and suet at feeders but spend much of their time gleaning tiny insects and larvae from bark and leaves. Starlings probe lawns for grubs while also eating fruit. Even many sparrows, often thought of as pure seed-eaters, regularly consume insects, especially during breeding season.
Gulls deserve special mention as extreme generalists. They eat fish, invertebrates, small rodents, garbage, and nearly anything else they encounter. Waterfowl like mallard ducks also qualify, feeding on aquatic plants, seeds, and small invertebrates.
Why Diets Shift With the Seasons
One of the most striking features of omnivorous birds is how dramatically their diets change throughout the year. Many songbirds in temperate regions eat mostly insects during spring and summer, then switch to mostly fruit during autumn. Hermit thrushes, for instance, get about 80 percent of their diet from fruit during fall migration. White-throated sparrows shift to around 60 percent fruit during the same period.
Spring and summer favor insect-heavy diets for a straightforward reason: breeding demands protein. Nestlings grow at extraordinary rates and need the amino acids that insects provide. Even species that eat seeds as adults will feed their chicks almost exclusively on insects and larvae during the first weeks of life. Scratching the ground for worms and larvae is such a deeply ingrained behavior in many bird species that it persists even in domesticated poultry.
In winter, when insect populations crash in colder climates, the same birds pivot to seeds, nuts, and dried fruit. This seasonal flexibility is a core survival advantage of omnivory. A strict insectivore either migrates or faces starvation when cold weather arrives. An omnivore can stay put and switch fuel sources.
How Their Digestive Systems Adapt
Omnivorous birds have a digestive trick that specialists lack: their intestines can adjust enzyme production based on what they’re eating. Research on chickens, bobwhites, and other omnivorous species found that 100 percent of avian omnivores tested can ramp up or down at least one digestive enzyme in response to dietary changes. When their diet is high in starch, they increase production of enzymes that break down carbohydrates. When protein intake rises, they boost protein-digesting enzymes instead.
This flexibility isn’t universal across all bird groups. The pattern of which enzymes respond varies between older and newer evolutionary lineages, suggesting that omnivory has evolved independently multiple times in birds rather than being inherited from a single ancestor.
How Cities Change What Birds Eat
Urban environments push omnivorous birds toward even broader diets. Crows, gulls, pigeons, and starlings thrive in cities partly because they’ll eat human food waste. Research on public feeding of urban birds found that bread alone accounts for about 67 percent of the food people offer, followed by meal leftovers. Almost no one provides animal-based food like mealworms.
This creates a nutritional mismatch. Bread is high in carbohydrates and low in the protein, fat, and micronutrients that birds need. Urban supplementary feeding also disproportionately attracts juvenile gulls and feral pigeons, which over time can shift local bird populations toward species that tolerate a poor-quality, human-provided diet. Birds that are naturally omnivorous have an easier time in cities, but “easy access to food” doesn’t necessarily mean “good nutrition.”
Birds That Seem Like Specialists but Aren’t
The line between omnivore and specialist is blurrier than it looks. Many birds classified as granivores (seed-eaters) or frugivores (fruit-eaters) regularly eat insects found on or near their primary food. A finch cracking seeds will readily eat a beetle larva hiding inside one. Frugivores commonly consume the insects associated with ripening fruit. These incidental animal foods can provide essential nutrients, particularly during molting or breeding, when protein demands spike.
Environmental pressures also push specialists toward omnivory. When a preferred food source disappears due to habitat loss, drought, or seasonal scarcity, birds that can expand their diet survive. This is one reason omnivory is so common among birds overall. It’s less a fixed category and more a spectrum, with most species landing somewhere between pure herbivore and pure carnivore, adjusting their position on that spectrum as conditions demand.