Changing fortunes of Bird Island Yesteryears of Michaelmas Cay

JANICE PICHON

Michaelmas Cay is a tiny, low-lying coral islet located 43km north-east of Cairns in the lagoon of the Great Barrier Reef. Sparkling azure waters and fine white sands surround a grassy platform which is crowned by a cloud of wheeling and screeching seabirds.

With a vegetated area of 1.8ha, this diminutive cay hosts an impressive and nationally important seabird rookery comprising up to 20,000 ground-nesting terns and noddies. The cay and the rookery depend on each other for their existence, with bird droppings bringing seeds of grasses and other low-lying plants, and also fertilising their growth. As grasses grow, they provide suitable habitat for nesting. If the birds disappear, the grasses that stabilise the sand will perish and, in time, the cay could be swept away by the sea, depriving the seabirds of their traditional breeding grounds.

In times past, the stability of this cay has been solely at the mercy of weather and sea conditions. However, since European settlement on the mainland, the equilibrium between the cay and its nesting seabirds has been tested by new forces. Particularly in the period between the mid1800s and the mid-1900s, the survival of “Bird Island” was imperilled by human activities.

Bêche-de-mer fishing

Commercial harvesting of bêche-de-mer (sea cucumbers) at Michaelmas Cay occurred between 1870 and 1905. Apart from its effect on sea cucumber populations, the fishing activity disturbed the island’s birds. A visiting group of naturalists in 1903 was bitterly disappointed to find most of the birds had deserted the cay due to the unsettling presence of a bêche-de-mer fishing camp. By the beginning of the 20th century, reef stocks of bêchede-mer were experiencing localised depletion and the industry dwindled.

Drilling

In May 1926, a party of eight set up camp on Michaelmas Cay for an ambitious scientific project to bore down into the island’s foundations. Organised by the Great Barrier Reef Committee in Brisbane, its goal was to discover the depth of the coral reef platform on which the cay sits.

Four months of drilling disturbed the physical environment along with the birdlife, although nothing seemed to quieten the perpetual cacophony of their squeals! Surprisingly, rather than avoiding the new inhabitants of their cay, the chicks were attracted to the crew, essentially to enjoy the shade cast by the men’s bodies, such protection from the sun being scarce on a treeless island.

The drilling program induced no long-term impacts, with the only visible trace being the bore hole marker which has proven a useful benchmark for tracking cay movement. Indeed, a visit to Michaelmas Cay two years later in 1928 by members of the Great Barrier Reef Expedition documented countless thousands of seabirds.

Providentially, the presence of the boring team threw light on other more harmful practices. In particular, the Cairns community was alerted to the plundering of the bird colony with egg collecting and senseless killing of birds: it was estimated that 50,000 eggs and several thousand birds were lost in a single month.

Guano extraction

Seabird islands develop rich beds of guano, the dried accumulation of years of bird excrement, along with their carcases and eggshells. In the era before the advent of commercial fertilisers, these phosphate-rich deposits were mined on many coral islands to fertilise mainland crops. In 1901, a 21-year lease was approved to remove guano at Michaelmas Cay together with adjacent Upolu Cay. Sustained guano mining took place up until 1940 and more than 1000 tons of deposits were removed from the two cays.

Guano mining involved clearing of cay vegetation to facilitate extraction of the phosphatic rock, along with major disturbance of the rookery. Over on the mainland, these operations caused mounting community concern about the eventual destruction of the island. Today, there is no visible evidence of these quarrying activities at Michaelmas Cay. However, some other Reef sites subject to more intensive mining still bear the scars, for example, Raine Island where the topography was completely altered.

Coral mining

Another resource extracted from Michaelmas Cay in the 1920s to 1930s was coral which was used to supply building materials and produce agricultural lime, a necessity for the neutralising the acidic soils of North Queensland sugar cane farms. In 1922, a lease for coral mining on the cay was issued, despite objection by the Cairns City Council. However, no monitoring occurred, and tons of coral materiel were taken from the prohibited zone above the high-water mark, directly impacting the birdlife.

The catastrophic effect of coral mining provoked objections from alarmed naturalists. Early evidence from extensive quarrying at a neighbouring cay showed reduced island height and almost no birds remaining. Nonetheless, a senior government official considered that the sacrifice of cays was justified by the agricultural benefits arising from improved cropping. Finally, the coral licence for Michaelmas Cay was revoked in 1934, and mining prohibited in 1937.

Pillaging wildlife

Over many decades, the bird colonies of Michaelmas Cay were regularly plundered by crews from passing ships and visitors from Cairns. Apart from killing the birds for meat, it was common practice to destroy all the eggs in a particular area, ensuring that any eggs collected on subsequent days would be freshly laid. Kerosene drumfuls of eggs were carted off the cay for consumption aboard or to be sold in Cairns where they were a favourite of cake bakers. Some visitors even used the cay for sport shooting or worse, killing birds for fun and smashing eggs.

The Cairns community became increasingly fearful that intensive egg collecting would wipe out complete generations of birds and jeopardise the rookery, along with its tourism potential. To protect its future, Michaelmas Cay was declared an animal and birdlife sanctuary in 1926. However, the cay was not monitored, and breaches occurred with egg harvesting being last reported in 1976.

Securing the future

The era of regulation and management arrived before irreparable long-term damage of Michaelmas Cay through resource exploitation. At the same time, the rise in reef tourism with larger and faster boats saw visitor numbers escalate, renewing the perils. Establishment of the Great Barrier Reef Marine Park and declaration of the cay as a Queensland National Park in 1975, complemented by site management plans, have prevented this “island of perpetual (bird) noise” being silenced.

The management challenge was to find solutions to allow visitation without damaging the cay and disturbing the birds, causing frightened adults to abandon their eggs or chicks to a certain death. Fencing the vegetated part and voluntary codes of conduct for tourism operators have proven successful. Specific measures were needed to limit bird disturbance from aircraft noise, with initially the banning of seaplanes and later planes overflying; the first time that airspace restrictions had been imposed on environmental grounds.

The fact that Michaelmas Cay is presently one of the top seabird nesting sites on the Great Barrier Reef is testament to the success of the island’s management. Through conservation practices, it has maintained a healthy environment, providing beneficial effects for biodiversity and tourism, as well as endowing the cay with greater natural ability to respond to future stresses. Today, Michaelmas Cay is welcoming new generations of visitors who share the island’s resources with the seabirds.