The grey squirrel (Sciurus carolinensis) is a familiar sight in parks and backyards across North America and in parts of Europe where it was introduced. This bushy-tailed rodent is often observed gathering seeds and nuts, leading many to believe its diet is exclusively vegetarian. However, the grey squirrel’s diet is often misunderstood, as its feeding habits extend beyond the acorns and sunflower seeds it is best known for. A common question arises when bird populations seem to decline: do grey squirrels eat birds and eggs?
Primary Diet of Grey Squirrels
The typical diet of the grey squirrel is overwhelmingly composed of plant matter, establishing it primarily as an herbivore. Their foraging activities center on the most abundant resources available throughout the year, generally derived from trees and plants. They consume large quantities of nuts, such as hickory, walnut, and especially acorns, which they either eat immediately or bury for later retrieval.
This tree-dwelling mammal also relies heavily on seeds, tree buds, and the flowers of various species in the spring. Fruits and berries become important food sources during the summer and early autumn. Grey squirrels are known to consume fungi, sometimes even truffles, which helps in the dispersal of fungal spores within the ecosystem. Despite this strong preference for botanical items, the species is technically classified as an omnivore.
The Reality of Avian Predation
Grey squirrels are documented to feed on birds, eggs, and nestlings, confirming their omnivorous nature. This behavior is considered opportunistic feeding rather than routine predation. When a squirrel finds an unattended or vulnerable nest, the eggs and young represent a sudden, high-quality source of protein and fat.
This search for protein is particularly important during the spring and early summer when squirrels are raising their own young and have higher nutritional demands. Documented cases and circumstantial evidence confirm that nest raiding is a genuine behavior. Local studies have attributed significant nest failures for certain open-nesting bird species to the presence of grey squirrels. The flexibility of the grey squirrel’s diet is also highlighted by its tendency to consume other animal matter, including insects, frogs, and occasionally carrion.
Specific Targets and Circumstances
The most vulnerable avian targets are those least able to defend themselves or escape, making eggs and nestlings the primary focus. Eggs are an easy source of concentrated nutrients, and their consumption is frequently reported. Helpless nestlings and young fledglings provide protein and offer minimal resistance to the agile squirrel.
Nest raiding often involves a stealthy approach, utilizing the squirrel’s climbing ability to access nests in tree cavities or on open branches. Because the squirrel forages at virtually all elevations, all types of nests, from ground-level to canopy-level, are at risk. In rare instances, a fully flighted adult bird may be preyed upon if it is injured or incapacitated.
Predation instances are frequently observed in suburban or urban environments where grey squirrels are abundant and bolder due to constant human presence. In these settings, squirrels may raid bird feeders, which can lead them to discover nearby nests. This behavior aligns with the spring and summer breeding seasons of birds, coinciding with the period of highest nutritional need for the squirrels themselves.