William Dampier made his first visit to New Holland in 1688. He explored this part of the coast on his second visit in 1699. Roebuck Bay is named after his ship. The sea is rich in invertebrate life some of which made a meal of HMS Roebuck’s planking. On the voyage home the worm-eaten ship was run ashore on Ascension Island before it could sink in open water. Dampier and his crew were marooned there for five weeks before being picked up and taken back to England.
There are two tides a day in the bay of about equal height (semidiurnal tides). The tidal range is massive exposing about 160 km2 of mudflat. The mud is rich in invertebrate life which provides food for the more than 100,000 migratory shorebirds that use the bay each year … HMS Roebuck’s revenge.
You can read just how incredibly rich <HERE>.
The north shore of the bay from close to Broome to Crab Creek is readily accessible. The Broome Bird Observatory is located close to the east end. The eastern and southern shore is a world of mangrove swamp and tidal creek more easily accessed from the water.
Tropical mudflats are a very different habitat than the tundra and steppes where the visiting birds breed. In summer the breeding grounds are so rich in mosquito larvae and other invertebrates that young shorebirds can feed themselves from the moment they hatch. On the other hand there’s no food available when the puddles are frozen or covered in snow so migration it is.
The migrants arrive in our southern spring and leave in autumn. They don’t all stay in the bay all summer, for some it’s just a staging post. Towards the end of their stay it is a great spot to quickly gain the weight that will be the fuel for the long flights ahead. Some birds do stay a year or two before making their first flight to the breeding grounds so there are some to be found all year.
The bay is Australia’s most important site for migratory shorebirds. The bay regularly supports more than 1% of the population of at least 22 different species. On any day during the wet season there are about 120,000 shorebirds out on the mud. The smallest is the Red-necked Stint. Much of the time it weighs about 25 to 30 grams (my little Fox Terrier weighs 10 kg, equivalent to 400 Stints). They will increase their weight by as much as 50% prior to departure on their 15,000 km journey to Siberia. The largest visitor is the Eastern Curlew at about 1 kg fuelled up and ready to leave.
Migration may seem like a very risky strategy but if a bird manages to make the return trip once it is likely to do it many more times. Red-necked Stints have been known to live more than 20 years by which time they will have flown further than a return trip to the moon.
The bay is also home to the rare Australian Snubfin Dolphin.
At approximately 140 animals, the snubfin dolphin population occurring in the 100 km2 study area within Roebuck Bay is one of the largest reported in Australia to date and should be considered of regional and, indeed, national significance. Despite this relative magnitude, the population is small by conservation standards. We also provide preliminary evidence of fidelity to the study area for a majority of individuals … <Murdoch University report>
Roebuck Bay is a unique place. It’s also a place under increasing pressure as Broome grows in size. Careful management is required if the natural values are going to be preserved.
This post has been updated following discussion with my good friend Chris Hassell, a Birdlife International researcher involved in full time study of shorebirds in the bay.
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