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Vulture Investors, Predators of the 90s: An Ethical Examination

The conservation of seabirds is the application of the principals of conservation biology to the protection of endangered seabirds. Seabird species are threatened by many human activities, including fisheries, pollution, explotation and from introduced species.

Threats edit

Interactions with fisheries edit

Fisheries also have negative effects on seabirds, and these effects, particularly on the long-lived and slow-breeding albatrosses, are a source of increasing concern to conservationists. The bycatch of seabirds entangled in nets or hooked on fishing lines has had a big impact on seabird numbers; for example, an estimated 100,000 albatrosses are hooked and drown each year on tuna lines set out by long-line fisheries.[1] [2] Overall, many hundreds of thousands of birds are trapped and killed each year, a source of concern for some of the rarest species (for example, only 1,000 Short-tailed Albatrosses are known to still exist).

Other fisheries have or do also pose a threat. Diving species, most especially the shearwaters and auks, are also vulnerable to gillnet fisheries. Studies of gill-net fisheries show that shearwaters (Sooty and Short-tailed) compose 60% of the seabirds kiled by gill-nets in Japanese waters and 40% in Monterey Bay, California in the 1980s,[3] with the total number of shearwaters killed in Japan being between 65,000 and 125,000 per annum over the same study period (1978-1981).[4] Seabirds are also thought to suffer when overfishing occurs.

Exploitation edit

The hunting of seabirds and the collecting of seabird eggs have contributed to the declines of many species, and the extinction of several, including the Great Auk and the Spectacled Cormorant. Seabirds have been hunted for food by coastal peoples throughout history—one of the earliest instances known is in southern Chile, where archaeological excavations in middens has shown hunting of albatrosses, cormorants and shearwaters from 5000 BP.[5] This pressure has led to some species becoming extinct in many places; in particular, at least 20 species of an original 29 no longer breed on Easter Island. In the 19th century, the hunting of seabirds for fat deposits and feathers for the millinery trade reached industrial levels. Muttonbirding (harvesting shearwater chicks) developed as important industries in both New Zealand and Tasmania, and the name of one species, the Providence Petrel, is derived from its seemingly miraculous arrival on Norfolk Island where it provided a windfall for starving European settlers.[6] In the Falkland Islands, hundreds of thousands of penguins were harvested for their oil each year. Seabird eggs have also long been an important source of food for sailors undertaking long sea voyages, as well as being taken when settlements grow in areas near a colony. Eggers from San Francisco took almost half a million eggs a year from the Farallon Islands in the mid-19th century, a period in the islands' history from which the seabird species are still recovering.[7]

Both hunting and egging continue today, although not at the levels that occurred in the past, and generally in a more controlled manner. For example, the Māori of Stewart Island/Rakiura continue to harvest the chicks of the Sooty Shearwater as they have done for centuries, using traditional methods (called kaitiakitanga) to manage the harvest, but now work with the University of Otago in studying the populations. In Greenland, however, uncontrolled hunting is pushing many species into steep decline.[8]

Introduced species edit

introduced species. Seabirds, breeding predominantly on small isolated islands, have lost many predator defence behaviours.[9] Feral cats are capable of taking seabirds as large as albatrosses, and many introduced rodents, such as the Pacific rat, can take eggs hidden in burrows. One species, the Guadalupe Storm-petrel, was driven to extinction by feral cats,[10], and many populations of seabirds have been greatly reduced.

Introduced goats, cattle, rabbits and other herbivores can lead to problems, particularly when species need vegetation to protect or shade their young.[11] Introduced plants can also have a deleterious effect, reducing nesting habitat.[12] The loss of nesting sites through habitat modification by introduced species intensifies competition between species for the remaining habitat, which can cause declines in smaller less aggressive species.

Human disturbance edit

Disturbance of breeding colonies by humans is often a problem as well—visitors, even well-meaning tourists, can flush brooding adults off a colony leaving chicks and eggs vulnerable to predators.

Pollution edit

 
This Crested Auklet was oiled in Alaska during the M/V Selendang Ayu spill of 2004.

The build-up of toxins and pollutants in seabirds is also a concern. Seabirds, being apex predators, suffered from the ravages of DDT until it was banned; among other effects, DDT was implicated in embryo development problems and the skewed sex ratio of Western Gulls in southern California.[13] Oil spills are also a threat to seabird species, as both a toxin and because the feathers of the birds become saturated by the oil, causing them to lose their waterproofing.[14] Oil pollution threatens species with restricted ranges or already depressed populations.

Ingestion of plastic flotsam is a problem for many other seabirds.[15] Once swallowed, this plastic can cause a general decline in the fitness of the bird, or in some cases lodge in the gut and cause a blockage, leading to death by starvation.

Some species such as the Barau's Petrel and the Newell's Shearwater, which nest high up on large developed islands, are victims of light pollution. Chicks that are fledging are attracted to streetlights and are unable to reach the sea. An estimated 20–40% of fledging Barau's Petrels are attracted to the streetlights on Réunion.[16]

Conservation edit

Protection of breeding colonies edit

The threats faced by seabirds have not gone unnoticed by scientists or the conservation movement. As early as 1903, Theodore Roosevelt was convinced of the need to declare Pelican Island in Florida a National Wildlife Refuge to protect the bird colonies (including the nesting Brown Pelicans),[17] and in 1909 he protected the Farallon Islands. Today many important seabird colonies are given some measure of protection, from Heron Island in Australia to Triangle Island in British Columbia.

Island Restoration edit

Island restoration techniques, pioneered by New Zealand, enable the removal of exotic invaders from increasingly large islands. Feral cats have been removed from Ascension Island, Arctic Foxes from many islands in the Aleutians,[18] and rats from Campbell Island. The removal of these introduced species has led to increases in numbers of species under pressure and even the return of extirpated ones. After the removal of cats from Ascension Island, seabirds began to nest there again for the first time in over a hundred years.[19]

Fisheries edit

Seabird mortality caused by long-line fisheries can be massively reduced by techniques such as setting long-line bait at night, dying the bait blue, setting the bait underwater, increasing the amount of weight on lines and by using bird scarers,[20] and their deployment is increasingly required by many national fishing fleets. The international ban on the use of drift nets has also helped reduce the mortality of seabirds and other marine wildlife.

Treaties and laws edit

The plight of albatross and large seabirds, as well as other marine creatures, being taken as bycatch by long-line fisheries, has been addressed by a large number of NGOs (including BirdLife International and the RSPB). This led to the Agreement on the Conservation of Albatrosses and Petrels, a legally binding treaty designed to protect these threatened species, which has been ratified by eight countries as of 2006 (namely Australia, Ecuador, France, New Zealand, Peru, South Africa, Spain, and the United Kingdom).[21]

References edit

  1. ^ BirdLife International/RSPB (2005) Save the Albatross: The Problem Retrieved March 17, 2006
  2. ^ Brothers NP. 1991. "Albatross mortality and associated bait loss in the Japanese longline fishery in the southern ocean." Biological Conservation 55: 255-268.
  3. ^ King, W.B. (1984) "Incidental mortality of seabirds in gillnets in the North Pacific" in Status and Conservation of the World’s Seabirds (Croxall, J.P, Evans, P.G.H. & Schreiber, R.W., eds) ICBP technical publication ISBN 0-946888-03-5 667-690
  4. ^ Ogi, H., (1984)Seabird mortality incidental to the Japanese salmon gill-net fishery” in Status and Conservation of the World’s Seabirds (Croxall, J.P, Evans, P.G.H. & Schreiber, R.W., eds) ICBP technical publication ISBN 0-946888-03-5 667-690
  5. ^ Simeone, A. & Navarro, X. (2002) "Human exploitation of seabirds in coastal southern Chile during the mid-Holocene" Rev. chil. hist. nat 75(2): 423-431 [1]
  6. ^ Anderson, A. (1996) "Origins of Procellariidae Hunting in the Southwest Pacific" International Journal of Osteoarcheology 6: 403-410
  7. ^ White, Peter; (1995), The Farallon Islands, Sentinels of the Golden Gate, Scottwall Associates:San Francisco, ISBN 0-942087-10-0
  8. ^ Burnham, W., Burnham, K.K., Cade, T.J., (2005) "Past and present assessments of bird life in Uummannaq District, West Greenland" Dansk Orn. Foren. Tidsskr. 99: 196-208 [2]
  9. ^ Moors, P.J. & Atkinson, I.A.E. (1984) "Alien predation on seabirds" in Status and Conservation of the World’s Seabirds (Croxall, J.P, Evans, P.G.H. & Schreiber, R.W., eds) ICBP technical publication ISBN 0-946888-03-5 667-690
  10. ^ A contempory account of the decline of the Guadalupe Storm-petrel can be found here - Thayer, J. & Bangs, O (1908) "The Present State of the Ornis of Guadaloupe Island" Condor 10(3): 101-106 [3]
  11. ^ Carlile, N., Proiddel, D., Zino, F., Natividad, C. & Wingate, D.B. (2003) "A review of four successful recovery programmes for threatened sub-tropical petrels" Marine Ornithology 31: 185-192
  12. ^ Flint, E. & Rehkemper, G. (2002) "Control and eradication of the introduced grass, Cenchrus echinatus, at Laysan Island, Central Pacific Ocean." in Turning the tide: the eradication of invasive species (proceedings of the international conference on eradication of island invasives) (Occasional Paper of the IUCN Species Survival Commission No. 27. Veitch, C. R. and Clout, M.N., eds) [4].
  13. ^ Fry, D. & Toone, C. (1981) "DDT-induced feminization of gull embryos" Science 213(4510): 922-924
  14. ^ Dunnet, G., Crisp, D., Conan, G., Bourne, W. (1982) "Oil Pollution and Seabird Populations [and Discussion]" Philosophical Transactions of the Royal Society of London. B 297(1087): 413-427
  15. ^ Pierce, K., Harris, R., Larned, L., Pokras, M., (2004) "Obstruction and starvation associated with plastic ingestion in a Northern Gannet Morus bassanus and a Greater Shearwater Puffinus gravis" Marine Ornithology 32: 187–189 [5]
  16. ^ Le Correa, M., Ollivier, A., Ribesc S., Jouventin, P., (2002) "Light-induced mortality of petrels: a 4-year study from Réunion Island (Indian Ocean)" Biological Conservation 105: 93–102 [6]
  17. ^ USFWS Pelican Island National Wildlife Refuge History of Pelican Island Retrieved September 2 2006
  18. ^ Williams, J.C., Byrd G.V.& Konyukhov, N.B. (2003) Whiskered Auklets Aethia pygmaea, foxes, humans and how to right a wrong. 'Marine Ornithology 31: 175-180 [7]
  19. ^ BirdLife International (2005) Stamps celebrate seabird return. Retrived August 12 2006
  20. ^ Food and Agriculture Organisation (1999) "The incidental catch of seabirds by longline fisheries: worldwide review and technical guidelines for mitigation. FAO Fisheries Circular No.937. Food and Agriculture Organization of the United Nations, Rome. [8]
  21. ^ Australian Antarctic Division Agreement on the Conservation of Albatrosses and Petrels Site Retrieved September 2 2006
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