Winter at Moulting Lagoon

by Sarah Lloyd

Swans at moulting lagoon

Swans at Moulting Lagoon

Conditions at Moulting Lagoon were exceptional this winter (2006), very different to those I'd experienced previously. This time there was no mirror-shiny sheet of water covering 3,000 acres, the extent of the lagoon. Instead the water was the lowest it's been in the 20 years since monitoring began. Water plants that are usually submerged were colouring the surface with flecks of green and vast areas of sandbanks that had hitherto been hidden were exposed, becoming more so as the tide receded during the morning.

Twice yearly assessments of the waterfowl and other birds are undertaken at Moulting Lagoon. The late summer count occurs just prior to the duck-shooting season and the winter survey is timed to evaluate the impact of the hunt. The ongoing monitoring is a requirement under the Ramsar convention to which the government is a signatory. Despite this, funding is decreasing annually and the assistance of volunteers is becoming ever more crucial.

Though summer counts are usually well attended and have, in recent years, attracted participants from New South Wales eager to spend a few days in this spectacular part of the island, the winter surveys are a different matter. Many birdwatchers leave Tasmania during the coldest months and this year some of the regular and most experienced counters were absent. Last year's novices were prematurely promoted to team leader status (a team consisted, in this case, of one volunteer (usually the 'expert') and one member of the staff from the local National Park office (who often knows just as much as the expert)). After the briefing session following the traditional Monday night pub meal, all field guides were out for a last minute check of the diagnostic features of some of the birds likely to be seen. But although we encounter thousands of birds (the lagoon supports up to 10,000 black swans) the variety of species, especially where the novices are sent, is not that great.

I love the biannual visits to the East Coast, especially when the weather's fine. This was the first winter count where I didn't have to chip ice off the windscreen before driving to the early morning rendezvous point. Instead, low cloud persisted for most of the morning and the Hazards, the granite mountains that provide a spectacular scenic backdrop to the lagoon, were shrouded in clouds. And there was not a breath of wind! It was quiet and serene and the birds seemed unusually settled, not spooked by our presence as they sometimes can be.

I was sent to the southern part of the lagoon, an area I've not seen before. Because of its proximity to the sea and its more marine environment it supports higher invertebrate loads and has a corresponding greater number of bird species, including some migratory waders that overwinter here. While the people at the northern part of the lagoon were counting the thousands of Black Swans that feed on the various water plants that grow in its shallow waters, I was walking the edge of Pelican Bay and Point Meredith, starting at Pelican Rocks and finishing at Swanick, where the lagoon drains into Great Oyster Bay.

In the section I was assigned to survey the opposite shore is well within sight and systematic counting is easy. In contrast, in the northern sections, where the distant shores are hardly visible, only imaginary lines across the water divide one search area from the next. We listened in to the usual two-way radio discussions about who should be counting all those swans that had just moved from bay to shore. (The buoys that had been positioned the previous year to facilitate the count had not survived the plundering of summer visitors.)

Great Crested Grebe
Great Crested Grebe

With spotting scope mounted on sturdy tripod, I counted methodically: Pied Cormorants, Silver Gulls, Pelicans, Pacific Gulls, Great Egrets, White-faced Herons, and GODWITS! I counted the single file of 37 Godwits many times, an excuse to watch these wonderful birds as they foraged in the shallow water adjacent to a sand spit. There were also Red-Necked Stints and Double-banded Plovers, a small flotilla of Hoary Headed Grebes and one Great Crested Grebe. I caught a glimpse, and then it dived and disappeared as grebes are wont to do.

Moulting Lagoon is one of ten sites in Tasmania listed under the Ramsar agreement as a wetland of international significance. It is the most important breeding and foraging habitat for Black Swans in Tasmania with numbers reaching over 14,000 in dry years. Many species of waterfowl, including Australasian Shelducks and Chestnut Teal, congregate in late summer; flocks of migratory waders, including Greenshank and Sharp-tailed Sandpiper visit the lagoon; it also has several rare and threatened plant species and unusual geological formations.

Seeing large numbers of birds in such a beautiful location is an amazing experience. For me, it's an opportunity to observe species, particularly grebes, I seldom encounter but for which I have a particular fondness.

Grebes are ancient birds that superficially resemble loons. This similarity is believed to be the result of evolutionary convergence for grebes are neither related to loons nor to any other group of birds.

Grebes are superbly adapted for an aquatic life. Their legs are situated well back on their body and their partially webbed feet and lobed toes propel them during their underwater pursuits of prey. But attributes for an aquatic existence are unsuitable for terrestrial activities; they are ungainly on land and some are unable to walk. Consequently their nests, floating platforms of plant material, are usually hidden in reed beds at the water’s edge. When they perceive danger they tend to dive rather than fly and when then do resort to flying they first skitter across the water, their toes acting like mini hydrofoils, before their fast flapping wings lift their bodies just above the surface.

Though reluctant to fly most don't lack the necessary skills or equipment to do so. In fact some grebes are migratory and fly long distances, usually at night. In Australia with its unpredictable climate and ephemeral wetlands grebes and other waterfowl must travel far and wide in search of suitable water bodies. In contrast, some species that live on remote lakes have lost the ability to fly and several species have become extinct.

The Atitlán Grebe, now extinct, was a flightless bird that as recently as 1990 inhabited just one (130 square kilometre) lake, the mile high remote Lake Atitlán in Guatemala. Its path to extinction is a sorry tale of destruction of its breeding habitat, inappropriate development, introduced species and genetic dilution. Sadly, it's a tale that's being repeated throughout the world, though on a different scale and with almost imperceptible rather than immediately disastrous consequences.

In 1965 a survey of the Atitlán Grebes found that their numbers had plummeted from a stable population of 200-300 to just 80 birds. The decline was attributed to the partial destruction of their breeding habitat; the reed beds that fringed the lake provided the perfect raw material for mat making.

Then the lake was developed as a tourist fishing resort. But there were no suitable fish! Large-mouth bass that liked the food that grebes liked and snacked on fluffy grebelets were brought to the lake to provide sport for the wealthy.

The threats continued: people from nearby cities wanting a holiday experience like no other ripped out the lakeside vegetation to create their own small beaches.

A natural disaster followed in 1976 when an earthquake caused the water level in the volcanic lake to fall by 6 metres, drying out the reed beds. Then in 1982, a national park game warden, one of a small team of people passionate about saving the bird, was shot by unknown assassins. In the politically volatile climate of Guatemala, no one was eager to replace him.

With its population already critically low a series of incidents ultimately sealed the birds' fate. Some were drowned in gill nets, others were disturbed by increasing boat traffic and then its cousin, the Pied-billed Grebe, an able flyer, arrived on the lake. Though just half the weight of the Atitlán Grebe, the more vigorous Pied-billed Grebe (some believe the Atitlán Grebe to be a subspecies of the Pied-billed) was able to compete for food. It also hybridised with the larger flightless bird, diluting the gene pool out of existence.

My recent visit to the south-eastern edge of Moulting Lagoon gave me cause for great concern. At the edge of the lagoon land is being subdivided and 'developed' and clearing of native vegetation continues, often illegally. Weeds are already a serious problem in some areas and are gaining a foothold in others. Whereas twenty years ago the hard-bottomed sand at the northern end of the lagoon supported flounder and shrimp, now the area is covered in 10 cm of boggy sand and these species have all but gone. The high levels of sedimentation mostly result from activities not necessarily in the immediate vicinity of the water. One wonders about the impact of the recent extensive plantings of grapevines near the northern shore, believed to be one of the largest vineyards in the southern hemisphere.

Moulting Lagoon will never again be the pristine productive waterway it was before white settlement when mammals, birds and particularly swans' eggs were an important food for the aboriginal people of the Oyster Bay Tribe. But neither should it have to deteriorate further. Only a strong commitment from the government and the community will ensure that Moulting Lagoon and its wildlife survive.

References:
- BirdLife International (2006) Species fact sheet: Podilymbus gigas. Downloaded from http://www.birdlife.org on 11/8/2006
- Forshaw, J. (Ed) (1998) Encyclopaedia of Birds. UNSW Press, McMahons Point, Australia.
- Fuller, E. (2000) Extinct birds. Oxford University Press, Oxford.
- Moulting Lagoon Game Reserve (Ramsar Site) Management Plan 2003 Parks and Wildlife Service Department of Tourism, Parks, Heritage and the Arts
- Sibley, D.A.. (2000) National Audubon Society The Sibley Guide to birds. Alfred A. Knopf, New York.

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