Bird conservation

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The extinction of the Dusky Seaside Sparrow was caused by habitat loss.
The extinction of the Dusky Seaside Sparrow was caused by habitat loss.

Bird conservation is a field in the science of conservation biology related to threatened birds. Humans have had a profound effect on many bird species. Over one hundred species have gone extinct in historical times, although the most dramatic human-caused extinctions occurred in the Pacific Ocean as humans colonised the islands of Melanesia, Polynesia and Micronesia, during which an estimated 750-1800 species of bird went extinct.[1] According to Worldwatch Institute, many bird populations are currently declining worldwide, with 1,200 species facing extinction in the next century.[2] The biggest cited reason surrounds habitat loss.[3] Other threats include overhunting, accidental mortality due to structural collisions, long-line fishing bycatch, pollution, competition and predation by nonnative invasive species,[4] oil spills and pesticide use and climate change. Governments, along with numerous conservation charities, work to protect birds in various ways, including legislation, preserving and restoring bird habitat, and establishing captive populations for reintroductions.

See Late Quaternary prehistoric birds for birds which disappeared in prehistoric and early historic times, usually due to human activity (i.e., starting with the Upper Paleolithic Revolution). For birds having gone extinct in modern times (since 1500), see Extinct birds.

Contents

[edit] Threats to birds

[edit] Habitat loss

The most critical threat facing threatened birds is the destruction and fragmentation of habitat.[5] The loss of forests, plains and other natural systems into agriculture, mines, and urban developments, the draining of swamps and other wetlands, and logging reduce potential habitat for many species. In addition the remaining patches of habitat are often too small to sustain bird populations, and these populations are increasingly vulnerable to localised extinction (see Island biogeography). The loss of tropical rainforest is the most pressing problem, as these forests hold the highest number of species yet are being destroyed quickly. Habitat loss has been implicated in a number of extinctions, including the Ivory-billed Woodpecker (disputed because of "rediscovery"), Bachman's Warbler and the Dusky Seaside Sparrow.

[edit] Introduced species

Arctic Foxes introduced to the Aleutian Islands devastated populations of auks; here a Least Auklet has been taken.
Arctic Foxes introduced to the Aleutian Islands devastated populations of auks; here a Least Auklet has been taken.

Historically the threat posed by introduced species has probably caused the most extinctions of birds, particularly on islands. Ninety percent of historical extinctions have occurred on islands, and most prehistoric human caused extinctions were insular as well. Many island species evolved in the absence of predators and consequently lost many anti-predator behaviours.[6] As humans traveled around the world they brought with them many foreign animals which disturbed these island species. Some of these were unfamiliar predators, like rats, feral cats, and pigs; others were competitors, such as other bird species, or herbivores that degraded breeding habitat. Disease can also play a role; introduced avian malaria is thought to be a primary cause of many extinctions in Hawaii.[7] The Dodo is the most famous example of a species that was probably driven to extinction by introduced species (although human hunting also played a role), other species that were victims of introduced species were the Stephens Island Wren, Poʻo-uli and the Laysan Millerbird. Many species currently threatened with extinction are vulnerable to introduced species, such as the Kōkako, Black Robin, Mariana Crow, and the Hawaiian Duck.

[edit] Hunting and exploitation

Humans have exploited birds for a very long time, and sometimes this exploitation has resulted in extinction. Overhunting occurred in some instances with naive species unfamiliar with humans, such as the moa of New Zealand,[8] in other cases it was an industrial level of hunting that led to extinction. The Passenger Pigeon was once the most numerous species of bird alive (possibly ever), overhunting reduced a species that once numbered in the billions to extinction.[9] Hunting pressure can be for food, sport, feathers, or even come from scientists collecting museum specimens. Collection of Great Auks for museums pushed the already rare species to extinction.

The harvesting of parrots for the pet trade has led to many species becoming endangered. Between 1986 and 1988 two million parrots were legally imported into the US alone. Parrots are also illegally smuggled between countries, and rarer species can command high prices.

[edit] Hybridisation

Hybridisation may also endanger birds, damaging the gene stock. For example, the American Black Duck has been often reported hybridising with the Mallard, starting a slow decline.

In captivity, some pheasant breeders favor the hybridisation of the Indian Peafowl with the Green Peafowl. This has damaged the captive stock, as some breeders falsely claim they have pure Greens when they are at least partially hybrid. Feral peafowl that live in certain Buddhist palaces and sacred garden in Southeast Asia are really hybrids and stamp makers have mistook hybrids for actual Green Peafowl [3].

[edit] Other threats

This Black-browed Albatross has been hooked on a long-line.
This Black-browed Albatross has been hooked on a long-line.

Birds face a number of other threats. Pollution has led to serious declines in some species. The pesticide DDT was responsible for thinning egg shells in nesting birds, particularly seabirds and birds of prey that are high on the food chain.[10] Seabirds are also vulnerable to oil spills, which destroy the plumage's waterproofing causing the bird to drown or die of hypothermia.[11] Light pollution can also have a damaging effect on some species, particularly nocturnal seabirds such as petrels.[12]

Seabirds face another threat in the form of bycatch; where birds in the water become tangled in fishing nets or hooked on lines set out by long-line fisheries. As many as 100,000 albatrosses are hooked and drown each year on tuna lines set out by long-line fisheries.[13] Migrating birds are also threatened by high rise buildings; an estimated one million birds a year are killed this way in the US.

[edit] Conservation techniques

Scientists and conservation professionals have developed a number of techniques to protect bird species. These techniques have had varying levels of success.

[edit] Captive breeding

Captive breeding, or ex-situ conservation, has been used in a number of instances to save species from extinction. The principal is to create a viable population of a species in either zoos or breeding facilities, for later reintroduction back into to the wild. As such a captive population can either serve as an insurance against the species going extinct in the wild or as a last ditch effort in situations where conservation in the wild is impossible. Captive breeding has been used to save several species from extinction, the most famous example being the California Condor, a species that declined to less than thirty birds. In order to save the California Condor the decision was made to take every individual left in the wild into captivity. From these 22 individuals a breeding programme began that brought the numbers up to 273 by 2005. An even more impressive recovery was that of the Mauritius Kestrel, which by 1974 had dropped to only four individuals, yet by 2006 the population was 800.[14]

[edit] Reintroduction and translocations

Reintroductions of captive bred populations can occur to replenish wild populations of an endangered species, to create new populations or to restore a species after it has become extinct in the wild. Reintroductions helped bring the wild populations of Hawaiian Geese from 30 birds to over 500. The Mauritius Kestrel was successfully reintroduced into the wild after its captive breeding programme.[14] Reintroductions can be very difficult and often fail if insufficient preparations are made, as species born in captivity may lack the skills and knowledge needed for life in the wild after living in captivity. Reintroductions can also fail if the causes of a birds decline have not been adequately addressed. Attempts to reintroduce the Bali Starling into the wild failed due to continued poaching of reintroduced birds.[15]

Species totally extinct in the wild have been reintroduced, such as the Tennasirim Green Peafowl into Malaysia [16]. However, sometimes the wrong form of bird is introduced and there is still some controversy regarding if the Malay, Javanese or Tennasirim form was introduced. There is some possibility that the birds used for the latter reintroduction were of the wrong form, as the publication had falsely claimed that the extinct Malaysian form was genetically identical to the still living in the wild Javanese form, when the two forms are in fact different [17]. Pictures of the birds near the Melaka Zoo match neither form, instead the birds look similar to the dullest race Pavo muticus spicifer [4]. However the picture has been identified to be an endangered or even extinct bird known as the Tennasirim Green Peafowl, which is related to spicifer. However, DNA tests have shown that the birds used in the reintroduction match with museum skins of birds that lived there, so either spicifer/Tennasirim was found in Malaysia as well or that both forms were used in the reintroduction.

Translocations involve moving populations of threatened species into areas of suitable habitat currently unused by the species. There are several reasons for doing this; the creation of secondary populations that act as an insurance against disaster, or in many cases threats faced by the original population in its current location. One famous translocation was of the Kakapo of New Zealand. These large flightless parrots were unable to cope with introduced predators in their remaining habitat on Stewart Island, so were moved to smaller offshore islands that had been cleared of predators. From there a recovery programme has managed to maintain and eventually increase their numbers.

[edit] Habitat protection

As the loss and destruction of habitat is the most serious threat facing many bird species, conservation organisations and government agencies tasked with protecting birds work to protect areas of natural habitat. This can be achieved through purchasing land of conservation importance, setting aside land or gazetting it as a national park or other protected area, and passing legislation preventing landowners from undertaking damaging land use practices, or paying them not to undertake those activities. The goals of habitat protection for birds and other threatened animals and plants often conflicts with other stakeholders, such as landowners and businesses, who can face economically damaging restrictions on their activities. Plans to protect crucial habitat for the Spotted Owl of North America required the protection of large areas of old growth forest in the western United States; this was opposed by logging companies who claimed it would cause job losses and reduced profits.[18]

[edit] Notes and references

  1. ^ Steadman D, (2006). Extinction and Biogeography in Tropical Pacific Birds, University of Chicago Press. ISBN 978-0-226-77142-7.
  2. ^ Worldwatch Paper #165: Winged Messengers: The Decline of Birds. Retrieved on 2006-07-21.
  3. ^ Help Migratory Birds Reach Their Destinations. Retrieved on 2006-07-21.
  4. ^ Protect Backyard Birds and Wildlife: Keep Pet Cats Indoors. Retrieved on 2006-07-21.
  5. ^ Gill, F. (1995). Ornithology. W.H Freeman and Company, New York. ISBN 0-7167-2415-4.
  6. ^ Blumstein, D., Daniel, J. (2005). "The loss of anti-predator behaviour following isolation on islands." Proceedings of the Royal Society of London Series B-Biological Sciences 272: 1663–1668.
  7. ^ Atkinson, C., Dusek, R., Woods, K., Iko, W. (2000). "Pathogenicity of avian malaria in experimentally-infected Hawaii Amakihi." Journal of Wildlife Diseases 36(2):197-204.
  8. ^ Holdaway, R., Jacomb, C. (2000). "Rapid Extinction of the Moas (Aves: Dinornithiformes): Model, Test, and Implications." Science 287(5461): 2250 - 2254.
  9. ^ Eckert, Allan W. (1965). The Silent Sky: The Incredible Extinction of the Passenger Pigeon. Lincoln NE: IUniverse.com. ISBN 0-595-08963-1.
  10. ^ Grier, W., (1982). "Ban of DDT and subsequent recovery of Reproduction in bald eagles." Science 218(4578): 1232-1235.
  11. ^ 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.
  12. ^ 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 [1].
  13. ^ Brothers NP. 1991. "Albatross mortality and associated bait loss in the Japanese longline fishery in the southern ocean." Biological Conservation 55: 255-268.
  14. ^ a b Jones, C.G.; Heck, W.; Lewis, R.E.; Mungroo, Y.; Slade, G.; Cade, T. (1995). " The restoration of the Mauritius kestrel Falco punctatus population." Ibis 137(Suppl.1): 173-180.
  15. ^ Putra, M. & Prins, H. (2000). "Status and distribution of the endemic Bali starling Leucopsar rothschildi." Oryx 34(3): 188–197.
  16. ^ Chiew, Hilary, The Star, Malaysia, The return of the Green peafowl, 11 January 2005. [2]
  17. ^ Mennig, Wolfgang, Die letzte Chance für den Ährenträgerpfau (The last chance for the Green Peafowl (Pavo muticus)?)German PDF
  18. ^ Simberloff, D. (1987). "The Spotted Owl Fracas: Mixing Academic, Applied, and Political Ecology." Ecology 68(4): 766-772.

[edit] See also

[edit] External links

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