Slender-billed Prion (Pachyptila belcheri)

Slender-billed Prion

[order] PROCELLARIIFORMES | [family] Procellariidae | [latin] Pachyptila belcheri | [authority] Mathews, 1912 | [UK] Slender-billed Prion | [FR] Prion de Belcher | [DE] Dunnschnabel-Sturmvogel | [ES] Pato petrel Picofino | [NL] Dunbekprion


Genus Species subspecies Region Range
Pachyptila belcheri SO widespread


Prions are a race of abundant small petrels from the Antarctic and subantarctic region with very similar plumages: a white body, bluish grey upperparts with a dark M on the back and upper sides of the wings when seen from above. Although there is considerable difference in measurements, the main difference between the species lies in the shape of the bills. These vary from small ‘pointed’ via ‘fulmarish’ to extreme broad. Characteristic are the lamellae along the sides of the palate in all species. These form a sieving structure to filter small food particles from the water. The development of these lamellae and grooves vary depending on the species. Bills of all Prions are bluish, except in the Broad-billed which has a blackish bill. Identification of the Prions at sea is very difficult. Therefore much of the pelagic distribution is unknown.
The taxonomy of the Prions is difficult and possibly not yet fully understood. It is mainly based on size and structure of the bill. But since there is a lot of intraspecific variability and intergradation between the recognized species and subspecies, the discussion on this topic is not closed yet. The list below shows the seven species that are accepted generally, including the recent separation of the MacGillivrayi’s Prion.

Physical charateristics

Apart from their small size, from afar their general appearance is similar to most procellariids being darker and patterned above and white below. Their most distinctive attribute are broadened mandibles with the upper mandible fringed with lamellae, which is used to filter plankton from the ocean. Very similar to Antarctic Prion but has paler blue-grey upperparts, whiter lores and broader, more conspicuous eyebrow stripe. Bill small and slender. The palest of all the prions. The distinctive white facial pattern is clearly discernible at close range.

wingspan min.: 55 cm wingspan max.: 57 cm
size min.: 25 cm size max.: 26 cm
incubation min.: 46 days incubation max.: 47 days
fledging min.: 43 days fledging max.: 54 days
broods: 1   eggs min.: 1  
      eggs max.: 1  


Southern Ocean : widespread. The Thin-billed Prion breeds the Crozet Islands and the Kerguelen Islands (French Southern Territories), the Falkland islands (Islas Malvinas) and Noir Island, Chile. Outside the breeding season it can be found over much of the Southern Ocean, including the coasts of South Africa, Australia and South America as far north as Uraguay and southern Peru


This marine species can usually be found over pelagic waters but will feed inshore or in shallow offshore waters during the breeding season.


They are annual breeders and lay one egg. Both parents incubate the egg for about 7 weeks. The young fledge after about 7 more weeks. This species builds it nest in a burrow in loose colonies.

Feeding habits

It feeds mostly on crustaceans with a heavy dependance on amphipods (particularly Themisto gaudichaudii). It can also take small fish and squid. It catches prey mainly by surface-seizing, dipping and pattering at night.

Video Slender-billed Prion


copyright: Laurent Demongin


This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern
Slender-billed Prion status Least Concern


Disperses widely over Southern Ocean after breeding, absent Mar-Sept; birds from Falklands apparently move W, gathering in large flocks off W South America, and ranging N to 15 degrees S; Indian Ocean birds move E, occurring regularly off Australia and New Zealand, but few records off S Africa.

Distribution map

Slender-billed Prion distribution range map

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