Squirrels primarily eat tree nuts, seeds and fruit, but their diets can also include flowers, bark, eggs, insects, leaves and even baby birds. Squirrels are opportunistic feeders, which allows them to consume human garbage when none of their favorite foods are available.
Squirrels are mostly herbivorous. Plants and fungal matter make up most of their diet. For some species, mushrooms and other fungi make up nearly half of their diet. American red squirrels mostly subsist on pine cones, while eastern gray squirrels favor nuts such as pecans, acorns and walnuts. Squirrels prey on baby animals and birds if they can catch them, but these are not a major part of their diet. Captive squirrels are primarily fed rodent block, a pet food designed for rats and mice, and fruits, nuts and seeds as secondary components.