The question of whether the common squirrel raids bird nests is a frequent concern for bird watchers and homeowners. Observations of these mammals near nesting sites often lead people to wonder if their seemingly harmless neighbors are predators. The straightforward answer, supported by documented field observations, is that squirrels occasionally raid nests to consume both eggs and young birds. This behavior is a natural, though often unsettling, facet of the ecosystem that highlights the complex feeding habits of these widespread rodents.
Are Squirrels Nest Predators
Squirrels native to North America, such as the Eastern Grey Squirrel (Sciurus carolinensis) and the Fox Squirrel (Sciurus niger), are confirmed nest predators. This predatory behavior is opportunistic, meaning they take advantage of easily accessible food rather than actively hunting for nests. They consume both eggs and newly hatched nestlings that are defenseless while parent birds are away foraging.
The impact of this behavior varies significantly depending on the specific location and local squirrel population density. In some isolated studies, researchers have attributed a significant percentage of nest failures, sometimes as high as 27% for specific bird species, to the presence of grey squirrels. However, large-scale monitoring efforts suggest that nest predation by squirrels on a population level is relatively minor, affecting only a small fraction of all nests observed.
The squirrels’ agility allows them to traverse the forest canopy and climb tall structures, putting all types of nests at risk, including those in tree cavities and open-cup nests high in the branches. For instance, a Fox Squirrel was documented consuming the eggs of a White-winged Dove. Parents of raided nests, especially songbirds, frequently abandon the site entirely rather than risk a confrontation with the rodent.
The Nutritional Motivation for Predation
The motivation behind a squirrel’s nest raid lies in its omnivorous diet, which requires more than just nuts and seeds. Squirrels are resourceful foragers and supplement their plant-based diet with animal matter when the chance arises. Bird eggs and nestlings are highly concentrated sources of protein, fat, and essential minerals.
These nutrient-dense meals are particularly important during specific periods, such as the breeding season when females require increased energy to produce and nurse their young. The shells of bird eggs also provide a ready source of calcium, a mineral often lacking in a typical diet of tree nuts and seeds. Taking advantage of available eggs and nestlings offers a significant nutritional boost.
This opportunistic feeding allows squirrels to maintain a flexible diet based on seasonal availability. When preferred foods like mast-crop nuts are scarce, or when energy demands are high, the concentrated nutrients in a nest become a valuable alternative resource. The behavior is a natural expression of the squirrel’s ability to maximize its food intake for survival.
Mitigating Nest Raids and Protecting Birds
Homeowners who want to protect nesting birds can implement several physical deterrents and make changes to their yards. The most effective strategy for birdhouses mounted on poles is the installation of a predator baffle. This smooth, wide barrier prevents climbing mammals from reaching the nest, and baffles have been shown to increase nesting success rates.
It is beneficial to place bird feeders away from nesting areas, as the seed and suet attract squirrels to the general vicinity. The concentration of squirrels near a food source increases the likelihood they will stumble upon an active nest. Trimming tree limbs that allow squirrels to leap onto a nest box or pole from above can also reduce access.
For nest boxes, securing a metal plate around the entrance hole helps prevent squirrels from chewing and enlarging the opening to gain entry. This makes it harder for the squirrel to access the interior and helps preserve the integrity of the nest box. Protecting nests involves making the path to the eggs and young birds difficult enough that the opportunistic squirrel moves on to find an easier meal.