Michaelmas Cay is a small vegetated coral cay (1.5 hectares in area and 3.5 m high) lying 43 km north-east of Cairns. The cay sits on the western tip of Michaelmas Reef; a mid-shelf reef formed by living coral animals and polyps which secret a limestone skeleton.
The cay itself was formed when fragments of the reef (coral, algae and shells) were washed to the shielded side of the reef by wave action and prevailing winds, to form a single bank. In the sheltered areas behind the sand bank, seeds deposited by birds and waves are able to establish, stabilising the cay and encouraging seabirds to roost and nest. Their droppings fertilise the sand and more plants are able to grow. Vegetation covers the centre of the cay.
Island Fauna
Michaelmas Cay is a major seabird nesting island in the northern Great Barrier Reef, and one of the most accessible along the entire reef for day visitors. 38 species of birds have been recorded on Michaelmas Cay (3 woodland species and 35 seabirds). The main breeding species are sooty terns, crested terns, common noddies and lesser crested terns. Occasional breeders include silver gulls, black-naped terns, bridled terns, black noddies, roseate terns and ruddy turnstones. Breeding activity and care of young occurs throughout the year, with sooty terns breeding every 8.5 months and others breeding annually.
Island Flora
Vegetation on the cay consists of a few low-growing plants (pioneer species) such as grasses, herbs, succulents and creepers. The plants cover an area of approximately 300 x 60 metres. Common species include: hairy spinifex (Spinifex hirsutus), stalky grass (Lepturus repens) and sea purslane (Sesuvium portulacastrum). The vegetation dries out during winter but the summer wet season usually results in plant regrowth.
Michaelmas Cay is monitored monthly by the Queensland Department of Environment and Heritage and works directly with the staff of tourist operations that visit the cay and utilise the waters around the reef to educate visitors not to disturb the natural history of the area, but still allow total enjoyment of this spectacular pristine environment.
