Pinnipeds, the group of marine mammals that includes seals, sea lions, and walruses, are primarily known for eating fish, squid, and crustaceans. While this holds true for most species, the diet of some seals extends beyond these typical marine foods. The answer to whether seals eat birds is definitively yes, though it is not a common behavior for all species. This avian predation is usually a specialized or opportunistic feeding strategy, adopted where seabirds are readily available.
Confirmation and Specific Examples of Predation
The most notorious avian predator among seals is the Leopard Seal (Hydrurga leptonyx), which inhabits the frigid waters surrounding Antarctica and the sub-Antarctic islands. These seals regularly include birds, particularly penguins, in their diet, making them a top predator in their ecosystem. They target various penguin species, including Emperor, King, Adélie, and Gentoo penguins, which represent a significant, high-energy food source.
Other seal species, while less specialized, also demonstrate this predatory behavior. Grey Seals (Halichoerus grypus), found in the North Atlantic, have been documented preying on seabirds like gannets and cormorants, often near breeding colonies. Brown Fur Seals (Arctocephalus pusillus) and some South American Sea Lions have also been observed hunting birds, including African penguins and black-necked swans. The consumption of birds by these species is generally considered opportunistic, often targeting young or fledging birds that are easier to catch.
Hunting Techniques and Methods of Capture
Seals that hunt birds employ specialized ambush and pursuit strategies. The Leopard Seal often patrols the waters beneath ice floes or near penguin colonies, remaining submerged while waiting for a bird to enter the water. This ambush technique is highly effective, catching flightless penguins during their vulnerable transition from land to sea. Once captured, the seal uses its powerful jaws to secure the bird. Since seals lack specialized shearing teeth, they violently shake the prey, repeatedly beating the carcass against the water surface to tear it into manageable pieces. When hunting surface-resting seabirds like gulls, seals must rely on a sudden, explosive burst of speed and agility underwater to secure the more buoyant and erratic prey.
Ecological Context and Dietary Significance
For most seal populations, the consumption of birds remains a small fraction of the overall diet, yet its ecological importance can be substantial. For generalist feeders like the Grey Seal, avian predation is opportunistic, increasing during the seabird fledgling season when young, inexperienced birds are abundant and easier to catch. This seasonal availability provides a high-energy meal when primary food sources are scarce.
The Leopard Seal, in contrast, is a specialized predator where birds form a regular and significant part of the adult diet. In the Antarctic winter, when sea ice expands, the seal’s diet shifts to heavily rely on accessible penguin colonies. This predatory behavior may also be a learned trait, often observed initially as play in sub-adults before developing into a specialized feeding niche for certain individuals. This individual specialization means a small number of seals can account for a large proportion of the total avian predation observed.