Diving petrels
| Diving petrels | ||||||||||
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Garnot Petrel ( Pelecanoides garnotii ) |
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| Systematics | ||||||||||
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| Scientific name | ||||||||||
| Pelecanoides | ||||||||||
| Lacépède , 1799 |
The diving petrels ( Pelecanoides ) or guillotine petrels are a genus belonging to the tube noses (Procellariiformes) of deep sea birds. These birds, which are widespread in the southern oceans, have perfected a diving way of life and developed similarities to the alken birds in convergent evolution , which is also the reason for the component " guillemot " of the alternative genus name, which stands for a genus of alkenes.
features
Diving petrels are 18 to 25 cm long and have a wingspan of 30 to 38 cm. Their weight is between 86 and 185 g. The plumage is gray or brown on the upper side, the underside is white. There is no such thing as gender dimorphism . Using the tube attachments on their beak , diving petrels can be clearly identified as members of the tube noses. In their overall appearance, however, they are more like a small representative of the alken , for example the crab grebe . The alks live in the northern hemisphere, while the diving petrels, together with the penguins, have created a comparable ecological niche in the southern oceans .
Like alks, diving petrels have a stretchable throat pouch that can serve as a food store. This feature has given them the generic name Pelecanoides , although the throat pouch is much less pronounced than that of the pelicans . The wings are short and strong and are used for propulsion when diving. In flight they flap their wings with high frequency. Often the locomotion to air and water alternates in quick succession; so diving petrels can fly into waves and continue their way on the other side without changing direction. The feet are webbed and the legs are set far behind the body. This is an adaptation for swimming, but allows for awkward locomotion on land.
The species are very similar to one another and practically indistinguishable at greater distances. The shape of the beak and above all the beak tubes are the only reliable identification features of the individual species.
distribution and habitat
Like many other tube noses, diving petrels prefer remote islands as breeding grounds. Two of the four species, the guillotine petrel and the magellan petrel , always stay close to the coast, while the other species also go to the open sea outside the breeding season. The largest colonies are located on islands in the Southern Ocean , for example on South Georgia , Tristan da Cunha and the Antipode Islands . But they also live on the islands off the coasts of Chile and Peru , in the Bass Strait and in the Cook Strait .
Way of life
activity
Like petrels , diving petrels only go ashore at night. By avoiding the mainland during the day and on bright full moon nights, they avoid the skuas , which they prefer to catch shortly after landing when they are relatively helpless. Diving petrels breed in large colonies, but are solitary at sea. During the rest phases they swim on the water surface; the foraging is done by flying or diving. In the event of a threat, they tend to flee by diving rather than flying.
nutrition
The main food of the diving petrel are pelagic living crustaceans , mainly krill , copepods and amphipods . Small fish and cephalopods , on the other hand, are only caught in exceptional cases. They mostly get their food while diving, reaching great depths and staying under water for several minutes.
Reproduction
Diving petrels breed in large colonies that can number thousands of pairs. These are mostly located directly on the coast; However, on inhospitable islands like South Georgia, diving petrels form small colonies even a few kilometers inland. In these regions they are largely protected from predators, as only a few other animals live in this sub-Antarctic habitat remote from the coast.
The birds visit the colonies a few weeks before the breeding season. This is also done by non-breeding young birds that spend the breeding season with their fellow species in the colony. The nest hole is dug in loose earth or guano . A tunnel up to 1.5 m long leads to the cave, the exit is usually hidden under a stone or in the vegetation. In this cave, the female lays a single, large, white egg, which is incubated by both partners for seven to eight weeks. The young birds are then fed a pre-digested food pulp and abandoned when they are eight weeks old. Although they still have remains of nestling down at this age, the young now fly out to sea alone.
Diving petrels become sexually mature at the age of two, which is much earlier than other tubular noses. Nothing is known about life expectancy, but it is likely to be relatively low given early sexual maturity.
Tribal history
The oldest fossil diving petrels were assigned to an unknown member of the genus Pelecanoides from the Pliocene of South Africa. Overall, fossil finds are too rare to be able to make statements about the evolutionary origin of diving petrels.
Systematics
The diving petrels have long been considered an independent family (Pelecanoididae) within the tubular noses . DNA comparisons showed, however, that the genus is closely related to the petrel genera Pterodroma (hook shearwater ) and Puffinus ( shearwater ), which means that petrels are paraphyletic in relation to diving petrels . In more recent publications, diving petrels are therefore assigned to petrels.
There are five types:
- Garnot Petrel ( Pelecanoides garnotii ) off the coasts of Peru and Chile
- Magellan petrel ( Pelecanoides magellani ) off the coasts of Patagonia and Tierra del Fuego
- Broad-billed Guillemot ( Pelecanoides georgicus ) subantarctic seas
- Guillemot ( Pelecanoides urinatrix ) widespread in southern temperate and sub-Antarctic seas
- Pelecanoides whenuahouensis an endangered species, described in mid-2018, thatbreedson Codfish Island near New Zealand.
Humans and diving petrels
As residents of sub-Antarctic islands who only visit their colonies at night, diving petrels had little contact with humans. Unlike other tubular noses, they never follow ships.
Nevertheless, humans have indirectly harmed the populations: The Garnot petrel of the Chilean coast used to create its breeding tubes in guano. The commercial exploitation of the guano supplies deprived it of its nesting sites. Today there are only a few thousand individuals on four islands. The IUCN therefore classifies the species as endangered ( endangered one).
The introduction of domestic cats , martens and rats as neozoa to previously mammal-free sub-Antarctic islands also had catastrophic effects . On Marion Island , a population of 2200 domestic cats has completely destroyed the guillemot and broad-billed petrel colonies. The damage done by cats is also evident on the Crozet Islands : several million pairs of the broad-billed petrel breed on the cat-free Île de l'Est, while the cats on the other islands have significantly decimated the originally large colonies. In order to prevent this mass extinction, to which other native animals also fall victim, there are extermination campaigns against the introduced animal species in some places. Especially on islands around New Zealand it has often been possible to exterminate rats and cats, thereby enabling the populations of diving petrels to recover.
Receipts and further information
Individual evidence
Most of the information in this article has been taken from the sources given under literature; the following sources are also cited:
- ↑ Richard O. Prum et al. A comprehensive phylogeny of birds (Aves) using targeted next-generation DNA sequencing. Nature, October 7, 2015; doi: 10.1038 / nature15697
- ↑ David W. Winkler, Shawn M. Billerman, Irby J. Lovette: Bird Families of the World: A Guide to the Spectacular Diversity of Birds. Lynx Edicions (2015), ISBN 978-84-941892-0-3 . Page 164 a. 165.
- ↑ Kagu, sunbittern, tropicbirds, loons, penguins, petrels IOC World Bird List, accessed December 19, 2019
- ↑ Johannes H. Fischer, Igor Debski, Colin M. Miskelly , Charles A. Bost, Aymeric Fromant, Alan JD Tennyson, Jake Tessler, Rosalind Cole, Johanna H. Hiscock, Graeme A. Taylor and Heiko U. Wittmer. 2018. Analyzes of Phenotypic Differentiations Among South Georgian Diving Petrel ( Pelecanoides georgicus ) Populations Reveal An Undescribed and Highly Endangered Species from New Zealand. PLoS ONE. 13 (6): e0197766. doi: 10.1371 / journal.pone.0197766
- ↑ Pelecanoides garnotii in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed January 31 of 2009.
literature
- Josep del Hoyo et al .: Handbook of the Birds of the World. Volume 1: Ostrich to Ducks. Lynx Edicions, 1992, ISBN 84-87334-10-5 .
- Michael Brooke: Albatrosses and Petrels across the World . Oxford University Press, 2004 ISBN 0-19-850125-0
