Birds exhibit complex behaviors when it comes to protecting their eggs and young. If you’ve ever seen a bird defending its nest from predators, you know they will fiercely guard their eggs and babies. But do birds ever eat the eggs of other birds? The answer is not so simple.
If you’re short on time, here’s a quick answer to your question: Some birds will opportunistically eat other birds’ eggs, but most species avoid it. Egg cannibalism does occur in certain situations when birds need extra nutrition or want to reduce competition over limited resources.
In this comprehensive article, we’ll take an in-depth look at the intriguing topic of egg eating among birds. We’ll discuss which species engage in egg cannibalism, the motivations behind this behavior, how common it is, and what factors influence birds to eat eggs from other nests.
Whether you’re a birdwatcher, biologist, or simply curious, read on to learn all about this fascinating aspect of avian behavior.
Which Bird Species Eat Other Birds’ Eggs?
Gulls
Gulls are notorious for eating other birds’ eggs. They often raid the nests of seabirds like terns, murres, and puffins to consume the eggs inside. For example, herring gulls and greater black-backed gulls along the New England coast have contributed to significant declines in tern populations by consuming up to 90% of tern eggs in some colonies.
Crows
American crows, fish crows, and northwestern crows frequently eat the eggs of smaller songbirds when given the chance. In one study, approximately 75% of real and artificial nests located were depredated by American crows within 10 days.
Their intelligence and adaptable behavior allow them to be formidable nest predators.
Jays
Jays like blue jays, gray jays, Florida scrub jays, and Steller’s jays eat eggs opportunistically as they find them. One study in Illinois found blue jays responsible for 65% of artificial nest predation events. As omnivores and smart birds, jays check various habitats for easy meals.
They raid other birds’ nests for protein-rich eggs that make nutritious snacks.
Owls
Different owl species like barn owls, barred owls, great horned owls, and eastern screech owls are avid predators of birds and eggs. One study found the remains and bands of over 50 different bird species in great horned owl pellets and nests.
As nocturnal hunters, owls use their spectacular vision and silent flight to swoop in and carry off adults, chicks, and eggs from nests at night.
Hawks
Accipiters like Cooper’s hawks and sharp-skinned hawks specialize in hunting other birds in woodlands. Though they mainly capture adult birds, sources show they can threaten eggs as well. For example, a Cooper’s hawk nest in Maine was found with the remains of a mourning dove and nearly 300 other bird eggs inside.
Eagles
Bald eagles and golden eagles are sometimes egg predators, though they mainly consume fish and mammals. During food shortages, these large raptors may raid nests for an easy meal. One study in Russia found white-tailed eagle nests containing the remains of over 45 bird species, including eggs from ducks, gulls, grouse, and corvids.
Why Do Some Birds Eat Eggs From Other Nests?
Birds exhibit a range of feeding behaviors, including consuming eggs from the nests of other avian species. This seemingly ruthless practice serves important purposes for the egg-eating birds.
Nutritional Needs
Eggs provide birds with a concentrated source of protein, healthy fats, and vital nutrients like calcium, phosphorus, and iron. Birds may raid nests to supplement their nutritional requirements, especially during demanding life stages like migration or breeding season when energy demands peak.
For example, herring gulls increase egg predation substantially while breeding, likely because eggs provide an efficient nutrition source for forming eggs of their own. Some tropical birds like toucans and trogons rely heavily on pirating eggs from tree-cavity nesting species.
Reducing Competition
Birds also attack the nests of competing species to eliminate threats to their resources. By eating eggs, birds not only gain a meal but also reduce the potential for rival birds to hatch and compete for limited food, water, nest sites, and other necessities in the habitat.
Highly territorial birds like European starlings frequently raid the nests of cavity-nesting competitors. This competitive edge allows them to effectively take over ideal nesting areas.
Opportunistic Foraging
Finally, some instances of egg consumption come down to opportunism. Birds like crows exhibit highly omnivorous, flexible diets – essentially consuming whatever prey items they happen to encounter. Unattended eggs in accessible nests present easy, vulnerable protein sources that crows capitalize on without necessarily targeting the eggs of competing species.
So while observing birds ruthlessly raiding nests can seem shocking, this behavior amounts to practical, survival-driven dietary strategies. Eggs provide the perfect package of compact nutrition, allowing birds to supplement their needs, best rivals, and take advantage of chance opportunities.
How Prevalent is Egg Cannibalism Among Birds?
Depends on Species
The prevalence of egg cannibalism varies widely between bird species. Some birds, like seagulls, are notorious egg eaters and will readily consume the eggs of their own and other species. Other birds, like doves and songbirds, almost never eat eggs.
A lot depends on the particular traits and behaviors of each species.
In general, birds that nest in colonies or crowded areas are more likely to eat eggs compared to solitary nesting birds. Large predatory birds like hawks and eagles are also frequent egg eaters. Scavengers such as crows and jays will eat eggs opportunistically.
On the opposite end, monogamous songbirds and pigeons almost never eat eggs thanks to their strong parental instincts.
More Common When Food is Scarce
Birds are much more likely to eat eggs when normal food sources are scarce. During times of famine or harsh weather, the nutrients in eggs become an attractive supplement to birds’ diets. Even normally gentle birds may eat eggs to avoid starvation when pickings are slim.
Research on gulls has found egg cannibalism rates over 50% higher in years with low food availability. Birds also eat more eggs after storms or cold snaps limit normal prey. So while egg eating is a fairly common bird behavior, it becomes much more prevalent when food is hard to find.
Nest Density Plays a Role
Besides food availability, the density of nests also impacts how many eggs birds eat. Species that nest in large colonies, like many seabirds, experience more egg cannibalism since eggs are everywhere.
For example, herring gulls in packed breeding colonies may eat over 25% of all eggs laid. But the same gull species nesting solitarily eat far fewer eggs. Easy access leads densely nested birds to view eggs as quick snacks. This contrasts solitary nesters who work hard to protect eggs.
What Factors Influence Egg Eating?
Bird Species
Certain bird species are more likely to eat other birds’ eggs than others. Larger predatory birds like crows, jays, magpies, and ravens frequently snack on eggs, especially when other food sources are scarce. Small songbirds typically do not eat other birds’ eggs.
Shorebirds that nest in colonies, like terns and gulls, might eat the eggs of their neighbors occasionally. Seabirds tend to be the most frequent egg eaters, possibly because their food sources can be sporadic.
Food Availability
Birds are more likely to eat eggs when their normal food sources are scarce. For example, insectivorous birds might switch to eating eggs in times of low insect abundance. Birds that eat fish or seeds may eat more eggs when fish stocks or seed crops are low.
Egg eating is essentially an alternative feeding strategy when a bird’s regular diet is unavailable.
Nesting Conditions
The availability of good nesting sites influences rates of egg eating. Birds that nest in close proximity in colonies have more opportunities to eat their neighbor’s eggs. Limited nesting space forces birds to nest closer together.
Predatory birds like crows also find it easier to raid the eggs of colonially nesting birds. Solitary nesting birds are generally safer from egg eating, but crowding can force them to nest closer to potential egg eaters.
Timing in the Breeding Season
Egg eating happens most frequently early in the breeding season before most eggs hatch. Once parent birds start incubating eggs and the chicks hatch, egg eating drops off. However, egg eating may increase again at the end of the breeding season as parents abandon their nests.
The early and late parts of the breeding season see the most egg predation overall.
Conclusion
While most birds avoid eating eggs from other nests, egg cannibalism certainly occurs in the avian world. Birds like gulls and crows are the most frequent egg-eaters, viewing unguarded eggs as quick snacks. When food is scarce or nests are too close together, the chances of egg predation increase.
Understanding the complex factors that influence egg eating gives us a window into the survival strategies of birds. Next time you see a bird near a nest, look for signs of this remarkable behavior. With a bit of luck and patience, you may witness nature’s cunning opportunists at work!
