Nombre en español: Albatros ceja negra

Nombre en inglés: Black-browed Albatross

Nombre científico: Thalassarche melanophris

Familia: Diomedeidae

El albatros de ceja negra (Thalassarche melanophrys) es una especie de ave de la familia de los albatros.

Taxonomía

El nombre científico de esta especie de albatros es Thalassarche melanophrys (Temminck, 1828), aunque ha sido clasificado anteriormente como Diomedea melanophrys. Recientes revisiones han reubicado esta especie en el género Thalassarche.​

Características biológicas

Los albatros de ceja negra, al igual que los demás albatros, presentan alas largas de gran envergadura, hasta 2,3 m, lo que les confiere una notable habilidad para el vuelo por planeo. Pueden recorrer grandes distancias y tienen la habilidad de pasar gran cantidad de tiempo en vuelo continuo sin posarse en tierra o agua. Sin embargo, también son buenas nadadoras y presentan una membrana que une sus dedos, lo que les facilita la propulsión en el agua, aunque no sean buceadoras como otras aves marinas. Se mueven escasamente en tierra. Pueden llegar a pesar hasta 3,8 kg y vivir hasta 50 años.

Características etológicas

Su vida es pelágica, no costera, es decir se desarrolla mayormente en el mar, y se acercan a la tierra solo para reproducirse. Habitan aguas de zonas de climas ventosos, ya que este elemento les es indispensable para efectuar el vuelo y desplazarse. Nidifican siempre en islas, ubican sus nidos en cuestas escarpadas vegetadas por hierbas, a veces en los acantilados costeros, y también en las playas planas cerca de la orilla.

La dieta de estas aves es carnívora, compuesta por diversos organismos marinos como calamares, crustáceos, medusas, pulpos y algunos peces. Hoy en día suelen alimentarse de los desechos de los buques pesqueros, lo que los pone en peligro de muerte al quedar atrapados en las redes o líneas de pesca o quedando expuestos para ser cazados fácilmente.⁴​ Este es un problema muy grave que ha provocado un descenso poblacional notable, lo cual ha motivado la realización de convenios entre países para proteger esta especie, que ha sido clasificada como en peligro de extinción. Esta especie ha sido cazado comercialmente desde el siglo XIX para obtener plumas, que eran usadas con fines ornamentales y como relleno de almohadones y colchones. A su vez los buques balleneros, cuando recalaban en las islas, recolectaban gran cantidad de huevos.

Distribución geográfica

Los albatros de ceja negra habitan la zona marítima desde el Trópico de Capricornio hasta la Antártida y nidifican en islas oceánicas en zonas circumpolares. Existen en este momento en el mundo 14 lugares de nidificación: las Islas Malvinas, las Georgias del Sur (ambos archipiélagos en litigio entre el Reino Unido y Argentina), isla de los Estados (Argentina); las Islas Diego Ramírez, Ildefonso, Diego de Almagro e Islote Evangelistas (Chile); las islas Crozet y Kerguelen (Territorios Australes Franceses); las islas Macquaire, Heard y McDonald Australia), e islas Campbell, Antípodas y Snares (Nueva Zelanda).​

Estas aves se registran en las colonias de reproducción entre los meses de septiembre y abril, realizan por lo tanto la nidificación en el verano austral. Hasta diciembre realizan la incubación de los huevos, que es llevada a cabo por ambos progenitores. Luego, hasta mayo los pichones aprenden a volar. Es la única especie de albatros que se reproduce anualmente, poniendo un huevo por año.

La gran mayoría de las parejas (aproximadamente el 60 % de la población total mundial) se encuentran en las colonias de las islas Malvinas, 20 % en las islas Georgias y 20 % en Chile, en el resto de las islas existen pocas parejas, por ejemplo, en las islas Heard de Australia se registró un aumento de 200 a 600 parejas en los últimos 50 años.⁶​ Sin embargo, la población en la mayoría de estas colonias se ha reducido drásticamente en las últimas décadas.

Black-browed albatross

The black-browed albatross (Thalassarche melanophris), also known as the black-browed mollymawk, is a large seabird of the albatross family Diomedeidae; it is the most widespread and common member of its family.

Taxonomy

Mollymawks are albatrosses in the family Diomedeidae and order Procellariiformes, which also includes shearwaters, fulmars, storm petrels, and diving petrels. These birds share certain identifying features. They have nasal passages that attach to the upper bill called naricorns, although the nostrils on the albatross are on the sides of the bill. The bills of Procellariiformes are also unique in that they are split into between seven and nine horny plates. They produce a stomach oil made up of wax esters and triglycerides that is stored in the proventriculus. This is used against predators as well as being an energy-rich food source for chicks and also for the adults during their long flights.^[4] The albatross also has a salt gland above the nasal passage which helps to remove salt from the ocean water that they imbibe. The gland excretes a high saline solution through the bird’s nose.

In 1998, Robertson and Nunn published their view that the Campbell albatross (Thalassarche impavida), should be split from this species (T. melanophris). Over the course of the next few years, others agreed, including BirdLife International in 2000, and Brooke in 2004. James Clements did not adopt the split,^[9] the ACAP has not yet adopted the split, and the SACC recognizes the need for a proposal.

The black-browed albatross was first described as Diomedea melanophris by Coenraad Jacob Temminck, in 1828, based on a specimen from the Cape of Good Hope.

Etymology

The origin of the name melanophris comes from two Greek words melas or melanos, meaning «black», and ophris, meaning «eyebrow», referring to dark feathering around the eyes.

Description

The black-browed albatross is a medium-sized albatross, at 80 to 95 cm (31–37 in) long with a 200 to 240 cm (79–94 in) wingspan and an average weight of 2.9 to 4.7 kg (6.4–10.4 lb). It can have a natural lifespan of over 70 years. It has a dark grey saddle and upperwings that contrast with the white rump, and underparts. The underwing is predominantly white with broad, irregular, black margins. It has a dark eyebrow and a yellow-orange bill with a darker reddish-orange tip. Juveniles have dark horn-colored bills with dark tips, and a grey head and collar. They also have dark underwings. The features that distinguish it from other mollymawks (except the closely related Campbell albatross) are the dark eyestripe which gives it its name, a broad black edging to the white underside of its wings, white head and orange bill, tipped darker orange. The Campbell albatross is very similar but with a pale eye. Immature birds are similar to grey-headed albatrosses but the latter have wholly dark bills and more complete dark head markings.

Range and habitat

The black-browed albatross is circumpolar in the southern oceans, and it breeds on 12 islands throughout that range. In the Atlantic Ocean, it breeds on the Falkland Islands, South Georgia and the South Sandwich Islands, and the Cape Horn Islands. In the Pacific Ocean it breeds on Islas Ildefonso, Diego de Almagro, Islas Evangelistas, Campbell Island, Antipodes Islands, Snares Islands, and Macquarie Island. In the Indian Ocean it breeds on the Crozet Islands, Kerguelen Islands, Heard Island, and McDonald Island.

There are an estimated 1,220,000 birds alive with 600,853 breeding pairs, as estimated by a 2005 count. Of these birds, 402,571 breed in the Falklands, 72,102 breed on South Georgia Island, 120,171 breed on the Chilean islands of Islas Ildefonso, Diego de Almagro, Islas Evangelistas, and Islas Diego Ramírez. 600 pairs breed on Heard Island, Finally, the remaining 5,409 pairs breed on the remaining islands. This particular species of albatross prefers to forage over shelf and shelf-break areas. Falkland Island birds winter near the Patagonian Shelf, and birds from South Georgia forage in South African waters, using the Benguela Current, and the Chilean birds forage over the Patagonian Shelf, the Chilean Shelf, and even make it as far as New Zealand. It is the most likely albatross to be found in the North Atlantic due to a northerly migratory tendency. There have been 20 possible sightings in the Continental United States.

Behaviour

Feeding

The black-browed albatross feeds on fish, squid, crustaceans, carrion, and fishery discards. This species has been observed stealing food from other species.

Reproduction

This species normally nests on steep slopes covered with tussock grass and sometimes on cliffs; however, on the Falklands it nests on flat grassland on the coast. They are an annual breeder laying one egg from between 20 September and 1 November, although the Falklands, Crozet, and Kerguelen breeders lay about three weeks earlier. Incubation is done by both sexes and lasts 68 to 71 days. After hatching, the chicks take 120 to 130 days to fledge. Juveniles will return to the colony after two to three years but only to practice courtship rituals, as they start breeding around the 10th year.

Conservation

Until 2013, the IUCN classified this species as endangered due to a drastic reduction in population.^[22] Bird Island near South Georgia Island had a 4% per year loss of nesting pairs, and the Kerguelen Island population had a 17% reduction from 1979 to 1995. Diego Ramírez decreased in the 1980s but has rebounded recently, and the Falklands had a surge in the 1980s probably due to abundant fish waste from trawlers; however, recent censuses have shown drastic reduction in the majority of the nesting sites there. There has been a 67% decline in the population over 64 years.

Increased longline fishing in the southern oceans, especially around the Patagonian Shelf and around South Georgia has been attributed as a major cause of the decline of this bird, The black-browed albatross has been found to be the most common bird killed by fisheries. Trawl fishing, especially around the Patagonian Shelf and near South Africa, is also a large cause of deaths.

Conservation efforts underway start with this species being placed on Convention on Migratory Species Appendix II, and Agreement on the Conservation of Albatrosses and Petrels Annex 1. It is being monitored on half of the islands, and most of the breeding sites are reserves. Heard Island, McDonald Island, Macquarie Island, and the New Zealand islands are World Heritage Sites. An initial Chilean census has also been completed.

Vagrancy

Although this is a rare occurrence, on several occasions a black-browed albatross has summered in Scottish gannet colonies (Bass Rock, Hermaness and now Sula Sgeir) for a number of years. Ornithologists believe that it was the same bird, known as Albert, who lives in north Scotland. It is believed that the bird was blown off course into the North Atlantic in 1967. A similar incident took place in the gannet colony in the Faroe Islands island of Mykines, where a black-browed albatross lived among the gannets for over 30 years. This incident is the reason why an albatross is referred to as a «gannet king» (Faroese: súlukongur) in Faroese. In July 2013 the first recorded sighting of a black-browed albatross in the Bahamas was made from the Bahamas Marine Mammal Research Organisation’s research vessel, off Sandy Point, Abaco. For four consecutive years from 2014 on, a bird – probably the same individual named Albert – has been sighted over Heligoland, and on the east coast of England.

Fuentes: Wikipedia/eBird/xeno-canto