Seabirds are a diverse group of avian species that spend most of their lives at sea but return to land for breeding. They are integral components of marine and coastal food webs. Like all wildlife, seabirds face natural predators, and understanding these interactions is key to appreciating their ecological dynamics.
Oceanic Hunters
Seabirds face various predators in their marine environment, including large fish and marine mammals. Sharks and large bony fish, such as tuna, can ambush seabirds from below the surface, especially when birds are resting or diving for food. Some large cephalopods may also opportunistically prey on seabirds.
Marine mammals also prey on seabirds. Seals and sea lions may target birds on the water during foraging dives. Orcas, or killer whales, are known to hunt a wide variety of prey, including seabirds. They have been observed killing seabirds, such as penguins, cormorants, and gulls, though they do not always consume them.
Land-Based Threats
When seabirds come ashore for nesting, they become vulnerable to terrestrial predators. Native land predators, such as foxes, can impact nesting colonies, preying on species like puffins and gulls. Large rodents and snakes also pose a threat, consuming eggs and chicks.
Introduced predators, however, pose a significant threat to seabird populations, especially on isolated islands. Species like rats, feral cats, dogs, and ferrets have caused declines and extinctions. Island seabirds often lack defenses against these non-native predators, having evolved without such threats. Rats commonly prey on eggs, chicks, and sometimes adult birds, particularly smaller burrow-nesting species. Feral cats are effective predators of ground-nesting seabirds, killing adults and young.
Aerial Attackers
Avian predators also hunt seabirds, often in the air or by ambushing them on land or water. Large raptors, such as eagles and falcons, may target seabirds in flight or on cliffside nesting sites. Gulls frequently prey on the eggs and chicks of other seabirds within crowded colonies, which can reduce breeding success.
Skuas are well-known avian predators of other seabirds. They employ kleptoparasitism, persistently chasing other seabirds until they drop or regurgitate their catches. Skuas also directly prey on smaller seabirds, chicks, and eggs, especially during the nesting season. For example, great skuas kill adult seabirds like puffins and gulls.
Ecosystem Dynamics of Predation
Predation is a natural process within marine and coastal ecosystems. It contributes to natural selection, favoring seabirds with traits that enhance survival against predators, and helps regulate populations. This balance ensures ecosystem health.
The introduction of non-native predators disrupts these natural dynamics. On isolated islands, seabirds evolved without terrestrial mammalian predators, making them vulnerable to introduced species like rats and cats. These introduced predators can lead to population declines, local extinctions, and broader ecological changes. Conservation efforts often involve managing or eradicating introduced predator populations to protect vulnerable seabird species and restore ecological balance.