by Mike Bingham
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Organisation for the Conservation of Penguins
Magellanic penguins are only found around the Falkland Islands and South America, but they are extremely numerous within these regions. The Falklands has a population well in excess of 100,000 breeding pairs, but this is small compared to populations in South America, which number around 900,000 breeding pairs in Argentina (Centro Nacional Patagónico) and 800,000 pairs in Chile (Environmental Research Unit). Breeding colonies range from the Golfo San Matías in Argentina, southwards around the islands of Tierra del Fuego, and northwards up the Pacific coast of Chile as far as Puerto Montt.
The Magellanic penguin is around 70cm long, and has an average weight of about 4kg. The head and upper parts are black apart from two broad white stripes beneath the throat; one running up behind the cheeks and above the eye to join the pinkish gape, the second running adjacent to the white underparts with which they merge above the legs. Females are slightly smaller than the males, but have similar plumage.
Penguins of the Genus Spheniscus, to which Magellanic, Humboldt and Galapagos penguins all belong, are much more loosely colonial than other penguins. They generally nest in burrows when soil conditions permit, and are consequently spaced much further apart than surface-nesting penguins. Magellanic penguin colonies in particular often extend over several kilometres of coastline, at densities ranging from 0.001 to 0.1 nests per sq.m.
Magellanic penguins are widely distributed throughout the region. They particularly like offshore islands with tussac grass or small shrubs, which are in abundance around the Falkland Islands, Tierra del Fuego and the Pacific coast of Chile. Such islands offer deep layers of soil for burrowing into, and dense vegetation offering protection from aerial predators. The Atlantic coast of mainland Argentina is much drier, and has less vegetation cover, but it is still home to around 650,000 breeding pairs, many of which nest above ground in surface scrapes or under bushes. Magellanic Penguins prefer to nest in burrows, but when soil conditions are unsuitable for burrowing, they will nest on the surface using whatever protection they can find.
Adults arrive at the nest sites to breed in September, and after a period of burrow excavation and repair, begin egg laying around mid October. Two equally sized eggs are laid 4 days apart, each with a weight of around 125g. Incubation takes around 40 days, with the female incubating the eggs for the first shift, while the male feeds at sea. He forages at distances of up to 500km away from the breeding site, before returning to relieve the female some 15 or 20 days later. She then goes to sea for a similar period, and when she returns, the two birds change over at regular intervals until the eggs hatch.
Both parents continue to brood the chicks in turn on a daily basis, for a period of about 30 days. Chicks are fed daily, with adults leaving the colony in early morning, and returning with food later the same day. Magellanic penguins mostly forage within 30km of the nest site during chick-rearing, except in the Falklands where longer foraging trips are forced by conflict with commercial fishing.
By the end of 30 days the chicks have developed their mesoptile plumage, and are able to venture out of the burrows. At this stage they look very different from the adults, being a browny grey above, and creamy white below. Living in burrows, chicks have good protection from both predators and cold weather while both parents are away feeding, and consequently they do not form creches in the way that most surface-breeding species do.
Whilst burrows offer good protection from most weather conditions, heavy rain can result in flooding of the burrows in certain areas. Chicks rarely drown in such circumstances, but often become wet and cold. Mesoptile plumage provides excellent insulation when dry, but it lacks the waterproofing qualities of the adult plumage and loses much of its insulation properties when wet. Consequently many chicks can die from hypothermia in such conditions. Living in burrows also means that both chicks and adults become infested with penguin fleas.
Despite the two eggs being of roughly equal size, adults give feeding priority to the first chick to hatch, resulting in a higher rate of mortality amongst second chicks. Nevertheless Magellanic penguins often rear two chicks successfully when sufficient food can be caught. Normal productivity ranges from 1.0 to 1.6 chicks per breeding pair in South America, but averages only 0.5 chicks per pair in the Falklands due to lack of protection from commercial fishing (See Revista Chilena de Historia Natural 2002: The decline of Falkland Islands penguins in the presence of a commercial fishing industry). Magellanic penguins do not relay if they loose their clutch.
When the weather is fine larger chicks often sit outside their burrow entrances, but will rapidly return to the safety of their burrows at the first sign of danger. Fledging occurs at 9 to 17 weeks of age, depending on food. Fledglings look similar to the adults, except for being greyer and lacking the clearly defined banding of the adults. Average fledging weight is around 3.3kg in South America, but only 2.7kg in the Falklands due to the difficulty adults encounter finding sufficient food for their chicks. Generally fledglings weighing less than 3kg are unlikely to survive, and juvenile survival in the Falklands is very low, resulting in an 80% decline since the onset of commercial fishing.
Freedom from parental responsibilities allows the adults to spend a period of time at sea, feeding up in preparation for their annual moult in March. Moulting takes 3 to 4 weeks, after which the adults leave the breeding site, and remain at sea until the following breeding season. Magellanic penguins can live to about 20 years of age.
Females may begin breeding at 4 years of age, but the males do not normally breed until they are at least 5 years old. This is quite possibly a consequence of there being more males than females, making it easier for inexperienced females to find partners than for inexperienced males. Magellanic penguins generally show strong site and mate fidelity, and pair-bonds are reinforced by allopreening.
Magellanic penguins are opportunistic feeders, taking roughly equal proportions of fish (such as Micromesistius australis, Sprattus fuegensis, Engraulis anchoita, Merluccius hubbsi, Patagonotothen sp., Austroatherina sp., Myxinus sp.), squid (Loligo gahi, Gonatus antarcticus, Moroteuthis ingens, Onychoteuthis sp.) and crustaceans (Munida gregaria). During chick-rearing, foraging trips are generally conducted on a daily basis during daylight hours, except in the Falklands where food is harder to find. Birds generally forage at depths of less than 50m, but on occasions may dive up to 100m. Winter foraging for prey often takes them way beyond their normal breeding range, with birds travelling as far north as the Bahia region of Brazil.
Magellanic penguins declined severely in the Falkland Islands during the 1980's and 1990's, which coincided with the rise of commercial fishing for squid and finfish. The current Falklands population (2002/03) stands at just 20% of its 1990/91 level, and this decline is still continuing. These declines have not occurred in nearby Chile or Argentina where colonies are protected from commercial fishing.
Comparisons of colonies in the Falklands, Chile and Argentina confirm that competition with commercial fishing is the major cause of the Falklands decline (See Revista Chilena de Historia Natural 2002: The decline of Falkland Islands penguins in the presence of a commercial fishing industry). Adult penguins in Chile and Argentina are able to return with food for their chicks on a daily basis, with foraging trips averaging 16 to 18 hours. By contrast adults in the Falkland Islands take approximately 35 hours to find the same amount of food.
With only half the amount of food being fed to chicks, lower chick survival rates result. Breeding success and chick survival rates are substantially higher in Chile (average 1.4 chicks per nest) than in the Falklands (average 0.5 chicks per nest). Chicks which do survive in the Falklands are also underweight (2.7kg compared to 3.3kg in Chile), giving Falklands fledglings little chance of surviving their first few weeks at sea. This huge difference in breeding success has resulted in a gradual decline in population, with insufficient chicks and juveniles surviving in the Falklands to replace natural adult mortality.
The breeding sites themselves also show the magnitude of the Falklands decline. In the Falklands, populations have declined so much that 80 to 90% of burrows are unoccupied or derelict. A Magellanic penguin in the Falkland Islands has no difficulty finding a suitable burrow. There are plenty of ready made ones whose owners have either died or moved elsewhere. In colonies in Chile, such as Magdalena Island, every inch of the colony is used by penguins. Even areas where the ground is unsuitable for making burrows are used, with Magellanic penguins nesting on the surface.
Some colonies along the Atlantic coast of Argentina have also experienced declines. These declines are due to a combination of commercial fishing, and oil pollution from the deliberate discharge of oily ballast water by tanker traffic.
By contrast to the Falkland Islands, the Argentinean fisheries not only affect penguin populations by reducing food abundance, but also through considerable bi-catch of Magellanic penguins in trawling gear. The reasons for this are unclear, but are probably related to differences in vessel type, trawl speed, net size and catchment areas.
Fishing vessels are not the only man-made hazard faced by Magellanic penguins in this region. An active offshore oil and gas industry make pollution from oil a constant risk to penguins. Oil is discharged into the sea both through accidental spillage, and through deliberate operational discharge of oily ballast water from tankers.
An estimated 40,000 Magellanic penguins are killed by oil pollution every year along the coast of Argentina, representing the main cause of adult mortality in this area. The commencement of oil exploration around the Falkland Islands could mean similar mortality amongst Falkland penguins, unless considerably higher standards to those employed in Argentina are demanded. Unfortunately early indications are not good. During a 5 month period of oil exploration around the Falklands in 1998, no less than three oil spills occurred, killing several hundred penguins, cormorants and other seabirds.
Magellanic penguins from both the Falkland Islands and South America face natural predators at sea, such as sea lions, leopard seals and orcas (killer whales). They also face predation of chicks and eggs by avian predators, such as gulls and skuas, but where the penguins nest in burrows, such predation is greatly reduced.
Magellanic penguins are also killed by crab fishermen around the remoter parts of southern Chile, the penguin carcasses being used to bait their crab pots. This probably has little impact on the overall population, but decimates the breeding sites that are affected.
Magellanic penguins are popular for tourism, but they are the most nervous of penguins. Visitors that approach breeding sites which do not normally have many visitors, will send the penguins scurrying into their burrows for safety. Magellanic penguins do readily adapt to regular visitation however, and become much less nervous with time. Nevertheless, careful control of tourism near Magellanic penguin burrows needs to be enforced, since burrows will readily collapse if walked over.
Simple fences keeping people just 2 or 3 metres away from burrows is all that is required, and this can benefit both penguins and tourists. Not only are the penguins protected from being crushed in their burrows, but they also rapidly learn that humans will not enter beyond the fence, and will confidently remain sitting outside their burrows for all to see. By contrast, visitors to unfenced sites will generally see little more than distant penguins scurrying away, or faces looking out from within their burrows.
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