The common image of a squirrel is that of a busy, bushy-tailed rodent focused solely on burying acorns and cracking open nuts, positioning them as harmless herbivores. However, the reality of their feeding habits is far more complex, revealing a dietary flexibility driven by survival and seasonal availability. The question of whether these familiar backyard residents engage in predation points to an unsettling aspect of their natural history.
Squirrels as Opportunistic Omnivores
Squirrels are classified as opportunistic omnivores, meaning their diet includes both plant and animal matter. This classification extends beyond merely eating insects or scavenged scraps; observation confirms that certain tree squirrel species, such as the Eastern Grey Squirrel and the American Red Squirrel, actively raid bird nests.
This behavior is not a primary feeding strategy but a strategic supplement, especially during the spring and summer nesting seasons when eggs and nestlings are abundant. They take advantage of easy, accessible protein sources that are often left unguarded. When a parent bird temporarily leaves a clutch, the nest becomes a vulnerable, high-calorie target.
The ability to process animal protein provides these rodents with a survival advantage, particularly where traditional food sources fluctuate. While their primary diet remains plant-based, the inclusion of animal matter demonstrates a successful adaptation to varied landscapes, including suburban and urban areas.
Nutritional Motivation for Predation
Squirrels engage in nest predation to meet specific nutritional requirements often lacking in a purely vegetarian diet. Nuts and seeds are rich in carbohydrates and fats but contain insufficient amounts of certain minerals and proteins. Bird eggs and nestlings offer a dense, complete source of these necessary nutrients.
Protein is especially sought after, becoming important for lactating female squirrels or those recovering from reproduction. Growing juvenile squirrels also benefit from the concentrated protein found in soft-bodied nestlings, which supports rapid muscle and tissue development.
Calcium is another nutrient desired by squirrels, especially for pregnant or nursing females who need it for bone health and milk production. The eggshells provide an easily digestible source of calcium, which is why squirrels may consume the entire clutch. The high fat content in eggs and young birds also delivers a concentrated burst of energy.
Identifying Vulnerable Species and Nests
The risk of predation is not equal across all avian species; it is influenced by the location and structure of the nest relative to the squirrel’s foraging patterns. Tree squirrels, such as the Eastern Grey Squirrel, are the most frequently observed predators given their arboreal lifestyle and close proximity to avian breeding sites. These species thrive in wooded and suburban areas, creating habitat overlap with common backyard birds.
Nests built in highly accessible locations face the greatest danger of being raided. This includes nests situated in low-hanging shrubbery, dense garden bushes, or those placed in artificial nest boxes with wide-open entrances. Cavity nests can also be easily accessed and exploited by agile squirrels.
Songbirds are particularly vulnerable because they tend to build open-cup nests or utilize easily accessible structures. Studies show that nest failures in species like tits and other small passerines can be attributed to squirrel activity. Their ability to forage at various elevations puts nearly all nesting birds at risk.
Deterring Squirrels from Nesting Areas
Homeowners can take several non-lethal steps to reduce the likelihood of squirrel predation on nests near their property. One effective strategy is to reduce the accessibility of potential launch points near known nesting sites. Trimming tree limbs that hang close to roofs, fences, or feeders eliminates easy pathways for squirrels to move between structures and nests.
Bird feeders, while beneficial for birds, can inadvertently attract a high local population of squirrels, increasing the risk to nests. Using squirrel-proof feeders helps manage the population. Placing feeders on smooth metal poles equipped with wide, conical baffles prevents squirrels from climbing up to the seed.
Another common method involves using capsaicin, the compound that makes chili peppers spicy, in bird seed mixes. Squirrels, like most mammals, are sensitive to capsaicin and find the taste unpleasant, but birds are unaffected. Treating bird seed with a capsaicin product can deter squirrels from lingering in the area, encouraging them to forage elsewhere.