Prion

What is a prion bird and how does it differ from other seabirds?

A prion is a small Antarctic seabird belonging to the genus Pachyptila and the family Procellariidae. These birds are characterized by their blue-gray upper plumage and whitish underparts.¹

Prions differ from other seabirds primarily through their specialized feeding adaptations. Unlike many other petrels, broad-billed prions possess a unique, flattened bill featuring internal strainers called lamellae, which function similarly to those found in ducks. Additionally, they have a distensible mouth floor that forms a pouch, allowing them to collect small marine invertebrates like crustaceans and squid. Their distinct feeding behavior, known as hydroplaning, involves skittering across the water’s surface with wings extended while using their feet for propulsion to dip their bills into the water.¹

Most species within this group nest in burrows on Antarctic and sub-Antarctic islands, with sizes ranging from the 20 cm fairy prion to the 27 cm broad-billed prion.¹

Where are prion birds typically found and what is their habitat like?

Prion birds are primarily found in the Southern Hemisphere, where they occupy cold-water regions. They are largely associated with Antarctic and sub-Antarctic islands, which serve as their primary breeding grounds.¹²

Habitat and Distribution

• Breeding Grounds: Prions typically nest in burrows located on islands throughout the Antarctic and sub-Antarctic regions. Some species, such as the broad-billed prion, have a more northerly distribution, breeding on islands situated between 35° and 60° S.²
• Marine Environment: These birds are highly pelagic, spending the vast majority of their lives at sea. They thrive in windy, cold-water latitudes, particularly near the Antarctic convergence—a zone of upwelling water between 40° and 60° S that is rich in krill and other marine invertebrates.¹
• Range: As a group, prions are considered relatively sedentary compared to other migratory seabirds, remaining largely within their cold-water range. They generally avoid the calm equatorial regions where wind—necessary for their flight—is scarce and food sources are less abundant.¹

What are the different species of prion birds and how are they classified?

It is important to clarify that the term “prion” refers to two entirely different concepts: a type of Antarctic seabird and an infectious protein particle associated with neurodegenerative diseases. The latter is not a bird or a living organism, but rather an abnormal protein structure.¹³

Regarding the avian species, prions are classified within the genus Pachyptila, which belongs to the family Procellariidae in the order Procellariiformes. While the genus includes several species, the provided information highlights two primary examples:¹

• Fairy prion (Pachyptila turtur): The smallest of the group, measuring approximately 20 cm (8 inches) in length.¹
• Broad-billed prion (Pachyptila forsteri): The largest of the species, measuring about 27 cm (11 inches) in length.¹

These birds are distinguished from other petrels by their specialized, flattened bills equipped with internal strainers known as lamellae, which allow them to filter-feed on small marine invertebrates.¹

What are the unique functions of the lamellae in a prion’s bill?

The lamellae in a prion’s bill serve as specialized strainers that allow the bird to filter-feed on small marine invertebrates, such as crustaceans and squid.¹

These structures are located on the upper mandible and function similarly to the strainers found in the mouths of ducks. During a feeding behavior known as “hydroplaning,” the bird skitters across the water’s surface with its wings extended and its feet providing propulsion. As it dips its bill into the water, the lamellae act as a filtration mechanism, trapping small prey while allowing excess water to pass through. This process is further supported by the bird’s thin, distensible mouth floor, which forms a small pouch to help collect and hold the filtered food.¹