Salvin's mollymawk (New Zealand)
Salvin's mollymawk or Salvin's albatross (Thalassarche salvini) is a typical medium-sized black and white albatross species. During the breeding season (August-April) they occur throughout coastal New Zealand, especially from Cook Strait south, and across to south-east Australian waters. After breeding it migrates to seas off Peru and Chile and occurs as a vagrant in the South Atlantic. A small population of a few pairs was reported breeding on the Crozet Islands in the Indian Ocean.
The Salvin's mollymawk is a large seabird of about 90 cm and 2.56 m across the wings and weighs 3.3 to 4.9 kg. They are, alongside the shy albatross, the largest of the mollymawk group. The adult bird has a pale grey face, upper throat, and upper mantle, creating a hooded effect, and has a silver-grey crown. Its back, upperwing, and tail are grey-black. The rump and underparts are white with a black thumbmark on underwing and black narrow leading and trailing edges on the wing and black wing tips. The bill is pale grey-green, with a pale yellow upper ridge, and a bright yellow tip on the upper mandible, and a dark spot on the tip of the lower mandible.
THREATS AND CONSERVATION
All breeding sites are free from mammalian predators, although an expanding New Zealand fur seal population at the Bounty Islands may be affecting breeding success. Salvin’s mollymawk was the second most common albatross species killed in the New Zealand fisheries 1998-2004 with demersal longliners and trawling operations responsible for the majority of mortalities. The conservation status of this species was moved from nationally vulnerable to nationally critical in 2013; the IUCN classifies this species as vulnerable. Bird banding and studies are underway, and all of the islands except for The Pyramid, and Forty-fours Island, which are privately owned, are nature preserves. In 1998, the Snares Islands and Bounty Islands were declared World Heritage Sites, and in 2006, the Western and Central Pacific Fisheries Commission adopted a measure to require bird bycatch mitigation measures south of 30°S. Banding shows that about 97% of adults survive from one year to the next, and the oldest birds would live for over 30 years.
The Salvin’s mollymawks breed in large, densely packed colonies, mainly on small rocky islands with little vegetation. They are monogamous with shared incubation and chick care. The nest is a pedestal of mud, feathers, bird bones, guano and debris accumulated from the immediate vicinity, and used and added to year after year. The single large white egg is laid in August-September, and incubated by both parents until early November (in about 65-75 days). The chicks fledge in February-April at about 115-130 days-old, and are independent at fledging.
As a typical albatross, Salvin’s mollymawks have perfected soaring flight. In strong winds they wheel effortlessly on their long, narrow, stiffly held wings. They use their webbed feet for swimming and as rudders when coming in to land. Their strongly hooked bills are used to grasp prey whilst the sharp edges of the upper mandible are used to slice it into manageable portions. However, albatrosses have a great capacity to extend the throat, and so can swallow large pieces of food. Salvin’s mollymawks feeds mainly on fish, squid, krill, salps and offal from fishing vessels taken from the surface. They rarely plunge or dive for food. Usually they are silent at sea, though may give harsh croaking when squabbling for food.
Mollymawks belong in the order Procellariiformes, along with shearwaters, fulmars, storm petrels, and diving petrels. They share certain identifying features. First, 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, unlike other tubenosed seabirds. The bills of Procellariiformes are also unique in that they are split into between 7 and 9 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 an energy rich food source for chicks and for the adults during their long flights. Finally, they have a salt gland that is situated above the nasal passage and helps desalinate their bodies, due to the high amount of ocean water that they imbibe. It excretes a high saline solution from their nose.
The Salvin’s, white-capped, shy and Chatham albatross were long considered the same species (a subspecies of Diomedea cauta (Gould, 1841)). However, following the transfer of D. cauta to the genus Thalassarche it was elevated to specific status. Molecular analysis has shown that it and the closely related Chatham albatross are sister taxa, and more distantly related to the shy.
Sources: Wikipedia, nzbirdsonline.org.nz