Pterodroma arminjonianaherald petrel(Also: Trindade petrel)

Geographic Range

Herald petrels are found in several, disjunct regions. The subspecies P. a. arminjoniana occurs in the south Atlantic near Trinidade and Martin Vaz Islands and in the Indian Ocean at Round Island in Mauritius. Some authorities do not place the Round Island populations in this subspecies, however. The subspecies P. a. heraldica is found in the southern Pacific, from northeastern Australia and throughout the tropical Pacific to Eastern Island. (del Hoyo, et al., 1992)


Herald petrels are found in the open ocean, only coming near or to land during breeding season near breeding colonies. They breed on oceanic islands or "stacks," on rocky cliffs or ledges up to 1000 meters high. They nest sometimes in dense vegetation on these islands. (del Hoyo, et al., 1992)

Physical Description

Herald petrels are from 35 to 39 cm long, about 318 g, and with wingspans of 88 to 102 cm. This species exhibits color polymorphism, with dark, light, and intermediate forms. Color morphs are similar in appearance to Kermadec petrels (Pterodroma neglecta), but with a pointed tail and more white on the underwing. Light morphs are similar to mottled petrels (Pterodroma inexpectata) because the patterns on their underwings form a loose, dark "M" shape of black patterns against a light underwing. Light morphs have less white on their faces than other Pterodroma species with white faces. Juveniles are similar to adults in appearance. They have pink legs and feet, with black distal portions to the feet, but the legs and feet may be entirely black in dark morphs. Their bills are black. Western south Atlantic populations (Trinidade petresl, P. a. arminjoniana) and Round Island petrels are larger than Pacific forms (P. a. heraldi). (Brooke, 2004; del Hoyo, et al., 1992)

  • Sexual Dimorphism
  • sexes alike
  • Average mass
    318 g
    11.21 oz
  • Range length
    35 to 39 cm
    13.78 to 15.35 in
  • Range wingspan
    88 to 102 cm
    34.65 to 40.16 in


Mated herald petrels cooperate to raise their young, remaining together for at least a breeding season. Otherwise, there is little know about mating systems in herald petrels. (Brooke, 2004)

Breeding season in herald petrels varies substantially across their range. They form loose colonies that are visited throughout the year by adults. Some breeding may occur throughout the year, with peak laying activity in October and April. They nest on the ground or in crevices under rocks. Females lay 1 egg that is incubated for 53 days. Young are fledged at about 100 days old. (Brooke, 2004; del Hoyo, et al., 1992)

  • Breeding interval
    Some breeding may occur throughout the year, with peak laying activity in October and April.
  • Breeding season
    Breeding season varies across their range.
  • Range eggs per season
    1 to 1
  • Average time to hatching
    53 days
  • Average fledging age
    100 days

Both parents incubate the egg and feed the young. They alternate incubation shifts of about 8 to 9 days long. Hatchlings are fed most frequently in their first 10 days, then less frequently through 75 days old, and much less frequently after that. Young are fed up to 138 grams of regurgitate at a feeding. (Brooke, 2004)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female


There is no information on lifespan in herald petrels. Other petrel species (Pterodroma) can live up to 20 years, herald petrels are probably similar. (Brooke, 2004)


Herald petrels are active during the day, seemingly foraging mostly during the morning when at breeding colonies. They are found at high densities at breeding colonies. Little is known of their behavior outside of breeding colonies. (Brooke, 2004)

Home Range

There is no information on home range in herald petrels, they range widely in search of food, both when breeding and when not at breeding colonies.

Communication and Perception

Herald petrels are vocal, using calls described as "ki"s, repeated every 10 to 12 seconds. (Brooke, 2004)

Food Habits

The food habits of herald petrels have not been reported, although they have been observed eating squid and may eat primarily squid. They seem to associate with Puffinus pacificus. (del Hoyo, et al., 1992)

  • Animal Foods
  • mollusks


Herald petrels are preyed on at nesting colonies by non-native mammalian predators, including feral pigs (Sus scrofa) and cats (Felis catus). They may have bred at lower elevations before being excluded to higher elevations and less accessible areas by these non-native predators. Feral pigs and goats (Capra hirca) have also destroyed vegetation on nesting islands, further restricting nesting opportunities. (BirdLife International, 2009)

Ecosystem Roles

It can be assumed that herald petrels are an important part of the pelagic seabird fauna, they seem to associate with Puffinus pacificus. (del Hoyo, et al., 1992)

Mutualist Species

Economic Importance for Humans: Positive

Herald petrels are important members of their oceanic avian community. Guano from their nesting colonies may be collected for sale.

Economic Importance for Humans: Negative

There are no negative effects of herald petrels on humans.

Conservation Status

Herald petrel subspecies have been assessed separately by the IUCN. Pterodroma a. arminjoniana (called Trinidade petrels) is considered vulnerable because populations are limited to several small island groups for breeding and are susceptible to threats to those colonies, such as non-native predators, oil spills, and stochastic events. The Round Island populations are also considered threatened by the Commonwealth environmental law in Australia. Pterodroma a. heraldica has a wider breeding range and is considered "least concern." Many breeding colonies are now protected and non-native predators and grazers on some islands have been eradicated, resulting in improved nesting habitat. (BirdLife International, 2009; del Hoyo, et al., 1992; Department of the Environment and Heritage, 2003)

Other Comments

Herald petrels are also known as Trinidade petrels. The subspecies are sometimes considered separate species and the Indian Ocean population has not been thoroughly assessed and may be a different species. Some authorities recognize 3 species instead of 1: Pterodroma atrata, nesting in the Pitcairn Islands in the south Pacific, Pterodroma arminjoniana in the south Atlantic, and Pterodroma heraldica in the south Pacific. Round Island populations may also be a different species, based on significant variation in mitochondrial DNA and information on morphology and parasitic lice faunas. (Brooke, 2004; del Hoyo, et al., 1992)

Pterodroma arminjoniana is named for an Italian vice-admiral, V.F. Arminjoni. (Brooke, 2004)


Tanya Dewey (author), Animal Diversity Web.


Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map


uses sound to communicate


young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat


uses smells or other chemicals to communicate


used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

  1. active during the day, 2. lasting for one day.

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


eats mollusks, members of Phylum Mollusca


Having one mate at a time.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


generally wanders from place to place, usually within a well-defined range.


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).


"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season


reproduction that includes combining the genetic contribution of two individuals, a male and a female


associates with others of its species; forms social groups.


uses touch to communicate


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


uses sight to communicate


BirdLife International, 2009. "Trinidade petrel (Pterodroma arminjoniana)" (On-line). BirdLife International. Accessed July 14, 2009 at

Brooke, M. 2004. Albatrosses and petrels across the world. Oxford: Oxford University Press.

Department of the Environment and Heritage, 2003. "Round Island Petrel (Pterodroma arminjoniana)" (On-line). Accessed July 14, 2009 at

del Hoyo, J., A. Elliott, J. Sargatal. 1992. Handbook of the Birds of the World, Volume I. Barcelona: Lynx Edicions.