Sea BirdsMost visitors to the Great Barrier Reef focus their attention under water, thinking colourful fish and exquisite coral gardens - but remember to make an effort to do some bird watching. The Sea Birds of this region are just as fascinating, and with many opportunities to do so and even combine the two why not?
Forty species of seabirds have been recorded on the Great Barrier Reef, 24 of them breeding in the region. An estimated 70 percent of these migrate or disperse after breeding, but as nesting occurs in all months of the year the area is always host to very large numbers of birds.
Good fishing and diverse, largely populated predator-free habitats make the Great Barrier Reef region the breeding choice for millions of seabirds. Some 75 of the 950 islands and rocks support known breeding colonies, many with several species together. The main colonies tend to be concentrated in the north and south of the Reef.
Seabirds will nest where there is suitable habitat - some may require bare sand, others low vegetation or shrubs and other trees. The majority nest on the ground in large colonies of sometimes thousands of birds packed closely together. It is thought that some species can only breed when large numbers gather together, providing some sort of hormonal cue. Some islands have been used by these birds for thousands of years, although the actual nesting site moves regularly, a strategy which allows vegetation to recover, and may prevent harmful diseases building up in the sand.
Tern nest vary from a simple scrape in the sand to clumps of vegetation lined with bits of coral, shells and coraline algal remains. Usually one egg is laid and incubated for 20-30 days depending on species. At first one adult at a time will remain to guard the chick while the other collects food. After a week or so most chicks join wandering crèches of youngsters, the parents locating them at feeding time by calling. The timing of independence for the fledged young varies; for sooty terns it is 70 days.
Nesting seabirds are vulnerable to a number of factors. Storms, particularly cyclones, cause eggs and chicks to die from exposure, inundation and erosion of nest sites, and desertion by adults. Seabirds usually forage within 10km of the nesting site but during bad weather may not be able to see their prey because of disturbed surface water, or be able to reach fish which have moved to deeper or distant waters. On a number of occasions the presence of large numbers of weak and dying seabirds have led to some being examined in case of disease. Usually they were found to have starved to death. Entire colonies of eggs and chicks may be deserted at times of bad weather.
Visiting Nesting Sites
While cyclones and storms cause obvious and dramatic damage to nesting colonies, these natural events are irregular. Far more damaging may be the regular, perhaps daily, low-level disruption by visitors. Eggs and chicks abandoned when their parents fly off as visitors approach, or aircraft fly low overhead, may die from exposure to heat or cold. They are also easy prey for silver gulls, numbers of scavengers having increased in association with human activities such as rubbish dumping and fish feeding.
Well-camouflaged eggs and chicks may even be crushed underfoot; shearwater burrows collapse easily. Frequent disturbance may lead to the nests being completely deserted, and in some cases sites, which have been in use for thousands of years, may be abandoned. The presence of people may also inhibit birds from starting to breed.
Please be very careful near seabird colonies and avoid them as much as possible. The presence of large numbers of birds does not mean that they are not vulnerable. Numbers of tropical seabirds are declining throughout the world and the Great Barrier Reef has one of the last, and possibly the largest undisturbed stocks. Preserving them is an international obligation; it is up to tour operators to explain this to their visitors.
There are a number of operators who visit colonies as part of their daily itinerary. Some include conducted guided walks on islands and sand cays, and the better operators do this with approval from Marine Parks, and under quite strict guidelines. If your more interested in the seabirds and would like to include this in an itinerary let us know and we can help guide you in the best direction.
Local Bird Colonies
There are 54 substantial seabird colonies in the Great Barrier Reef, 26 of them, with 23 species, in the Northern Region and 22(18 species) in the southern region.
The five islands with greatest numbers of nesting seabirds are, in order, North West Island, which is in the Capricorn section, nearby Masthead and Heron Islands, Raine Island, near the tip of Cape York, and Michaelmas Cay which is accessible from Cairns.
The island with the greatest number of nesting species (17) is Raine Island. It is the northernmost breeding island for wedge-tailed shearwaters and the only Australian breeding site for Herald Petrels. It was the only breeding island for red-tailed tropic birds in Eastern Australia until a few pairs began nesting on Lady Elliot Island in 1993.
Pelicans nest on islands of the northern and southern Great Barrier Reef, breeding in the winter, in the north. Of all seabirds, they are the most easily disturbed, the entire colony sometimes deserting. Please do not approach nesting pelicans. Roseate terns, black-naped terns, little terns and frigatebirds are also very easily disturbed.
Michaelmas Cay is one of the most important seabird nesting sites of the Northern Great Barrier Reef and the southern limit of sooty tern breeding on the reef. Main breeding species, in order of numbers are sooty terns, common noddies, crested and lesser-crested terns. Silver Gulls, black-naped terns, bridled terns, black noddies and roseate terns have also nested there.