The Snow Petrel (Pagodroma nivea) is an all-white seabird uniquely adapted to the rigorous environment of the Antarctic. This small, graceful petrel is considered a true Antarctic endemic, rarely venturing north of the pack ice. It is one of the most southerly-distributed vertebrates in the world, with some nesting colonies found hundreds of kilometers from the open ocean. The petrel’s survival depends entirely on its specialized feeding behavior and its ability to locate prey in the vast Southern Ocean.
The Primary Components of the Snow Petrel Diet
The diet is concentrated on high-energy, marine prey available near the Antarctic sea ice, primarily consisting of crustaceans, small fish, and cephalopods. Antarctic Krill (Euphausia superba) is a highly significant food source, especially for breeding birds, due to its abundance and rich lipid content. Krill are often concentrated in the productive waters around the ice edge, making them an accessible target during the austral summer.
Small fish, particularly myctophids (lanternfish), form a substantial part of the petrel’s intake. A species like Electrona antarctica provides a dense source of calories. These small fish undertake daily vertical migrations, rising closer to the surface at night, which makes them vulnerable to petrels active during twilight hours.
Cephalopods, specifically small squid, contribute to the overall diet, though typically in lesser quantities than fish or krill. The Snow Petrel is also an opportunistic feeder, supplementing active hunting with scavenging. This includes feeding on carrion, such as the remains of dead seals, whales, or penguins, and placentas left after seal births on the ice.
Specialized Foraging and Hunting Techniques
The Snow Petrel’s hunting methods are closely tied to the sea ice, which serves as both a foraging platform and prey habitat. The birds associate strongly with pack ice and icebergs, often perching on floes to rest or survey the water. They primarily employ surface seizing, flying low over the water to quickly grab prey at or just below the surface without fully submerging.
The pack ice concentrates prey like krill and fish in the marginal ice zone. Petrels target areas with intermediate sea-ice concentration, typically between 30 and 60 percent, where upwelling and productivity are high. This preference centers their foraging activities around the dynamic outer edge of the sea ice.
A remarkable adaptation is the petrel’s strong sense of smell, which helps them locate food in the expansive ocean. They detect volatile compounds, such as dimethyl sulfide (DMS), released by phytoplankton consumed by their prey. This ability allows them to find patchily distributed food sources over great distances, acting as a chemical compass to productive feeding grounds.
Seasonal Changes in Food Consumption
The Snow Petrel’s diet and foraging behavior show distinct changes linked to the Antarctic seasons and their breeding cycle. During the austral summer breeding season, the diet must be energy-dense to fuel chick rearing. Foraging adults focus on delivering high-lipid stomach oil to their chicks, derived from rich prey, particularly krill and lanternfish.
The distance petrels travel to find food shrinks during the brood-guard phase, when they must return to the nest frequently. This constraint means they rely on the most accessible, concentrated food sources near the coast. The high-demand period of chick feeding thus favors easily captured, calorie-rich prey.
In the non-breeding winter months, petrels disperse over a much wider area, sometimes traveling thousands of kilometers. As daylight decreases, their activity shifts, with an increase in nocturnal feeding. This suggests they rely more heavily on vertically migrating prey, like myctophid fish, which rise nearer the surface in the dark.