The Great Barrier Reef has earned its place as one of the great wonders of the world. Visible from space, it is 2,300 km long and comprises of 2900 reefs and 900 islands to explore.
The Great Barrier Reef started to develop approximately 600,000 years ago and a combination of physical and biological factors made conditions suitable for the growth of many types of coral species (450 known hard coral and 150 soft coral species) over geological time.
Heron Island forms part of the Capricorn Bunker group of reefs located at the southern end of the Great Barrier Reef. The vegetated cay island was named after the bird species, the reef heron, recently renamed the eastern reef egret (Egretta sacra). It has taken 11,000 years to develop.
The reef around Heron Island is a type of shelf reef. Its location and exposure to the elements: waves, wind, ocean currents, climate and extreme weather events, have contributed to the type of coral, plant and animal species that inhabit the reef. Induced pressure from animal activity, for example, grazing and colonisation, play a part in its continual growth.
Heron Island attracts a population of 900 of the 1625 species of fish inhabiting the Great Barrier Reef, for example, parrotfish, butterfly fish, trevally, wrasse, triggerfish and sea perch.
Parrotfish are interesting to observe. Some researchers have made mistakes in the past, identifying species due to an anomaly not apparent in other fish species. For instance, the ability of parrotfish to change gender (sequential hermaphrodite) and colour (polychromatism) throughout their lives. Most species start as plain coloured, small females (initial phase) and at certain points in their lives, transform into bright coloured, large males (terminal phase).
The parrotfish diet consists of algae, scraped off coral by using specialised teeth. The coral remains are excreted from the fish as sand. Research studies estimates these fish produce 30% of the sand around reefs and are one of the marine animals that play an important role in maintaining coral reef health.
At night some parrotfish species have been observed to envelope themselves in a cocoon of mucous. Apparently, the cocoon masks their scent from reef predators, like the moray eel (Family Muraenidae).
Nests made by wedge-tailed shearwaters (Ardenna pacifica), bridled tern (Onychoprion anaethetus) and the black noddy (Anous minutus) bird species can be spotted all over the island. The nesting burrows of shearwaters, shelter chicks waiting for their parents to return with food. Other species that live and breed on the island all year round include the buff banded rail (Gallirallus philippensis), the eastern reef egret (Egretta sacra), bar shouldered dove (Geopelia humeralis), black-faced cuckoo-shrike (Coracina novaehollandiae), capricorn silver eye, sacred kingfisher (Todiramphus sanctus), white-bellied sea eagle (Haliaeetus leucogaster), the silver gull (Chroicocephalus novaehollandiae), and migratory and visiting bird species. Black noddies are the pretty black and white birds that nest in the pisonia trees (Pisonia grandis).
These forests of pisonia trees produce a sticky sap, which can unfortunately, trap black noddies, supplementing the cycle of nutrients from guano and plant material. You can also find screw palms, casuarina, she oak and other plant and grass species as you wander around the island.
If you’re visiting Heron from November to January, loggerhead turtles (Caretta caretta) and green turtles (Chelonia mydas) make their way slowly onto beaches at night to lay their eggs. The turtle’s sensitivity to any artificial light (torches etc.) can distract or disorientate them. Moving too close to a nesting turtle might also cause them to panic, so it is recommended to maintain a safe distance of approximately 10 metres away. Just listening to them breathing in the darkness while they lay their eggs is an amazing experience.
Heron Island is but a small microcosm of the Great Barrier Reef, which forms the biggest tropical Marine Reserve and the largest protected World Heritage Area. It may have taken its time to develop into the extraordinary beauty it is today, but wasn’t it well worth the wait.
Please take a look at the University of Queensland’s Centre for Marine Studies link for a bird’s eye view of Heron Island.
Written by Gabrielle Ahern
Salty Wave Blue – Into all things ecology.
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Photographic Field Guide: Birds of Australia. An Australian Museum / Reed New Holland Publication. Text by Jim Flegg. 2006. Second Edition.
These links provide some great views, photographs, videos and information about Heron Island and the Great Barrier Reef.
Great Barrier Reef Marine Park Authority
Great Barrier Reef Marine Park Authority
Onboard – The Tourism Operators Handbook for the Great Barrier Reef
Heron Island – Great Barrier Reef
Caitlin Seaview Survey – An underwater view of the coral reefs around Heron Island