coastal and marine natural values of the kimberley - wwf - Australia

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44. Coastal and Marine Natural Values of the Kimberley6.9 ESTUARIES ANDMIGRATORY BIRDSNorth west Australia is internationallyimportant for a diversity of migrantshorebirds. To place this into perspective,a February 2004 Australian WadersStudy Group expedition to Eighty MileBeach recorded a staggering 2.88 millionOriental Pratincoles Glareola maldivarum.Up until this time, the official East Asian-Australasian flyway population estimatewas 67,000 (Straw, 2004).The region’s Ramsar sites alone supportvery significant proportions of theinternational flyway populations ofseveral species, but particularlyBar-tailed Godwit Limosa lapponica,Terek Sandpiper Xenus cinereus,Grey-tailed Tattler Heteroscelus brevipes,Great Knot Calidris tenuirostris,Red-necked Stint Calidris rufi collis,Greater Sand Plover Charadriusleschenaultii and Oriental PloverCharadrius veredus (Table 8). Otherspecies also occur in internationallyimportant numbers but may not appearin this table, as they are numericallyless abundant but may nonetheless beimportant.There are also significant numbersof shorebirds distributed throughoutthe estuaries, bays and islands of theKimberley. King Sound is of particularnote as it is the most extensive areaof mudflat in the region. Although thedensity of birds is not as high as inRoebuck Bay (Danny Rogers, AustralianWader study Group pers comm.), itnevertheless supports a very large numberof shorebirds.A gathering of 2.88 million Oriental Pratincoles Glareola maldivarum in the Ramsarsite at Eighty Mile Beach in February 2004. Photo by Chris Hassall.SpeciesRoebuckBayEighty MileBeach (northernend only)Total %flywayBlack-tailed Godwit Limosa limosa 1344 1344 0.9Bar-tailed Godwit Limosa lapponica 24245 47179 71424 44.6Little Curlew Numenius minutus 2552 2552 1.4Whimbrel Numenius phaeopus 572 572 1.0Eastern Curlew Numenius madagascariensis 550 550 1.4Common Greenshank Tringa nebularia 2916 2916 2.9Terek Sandpiper Xenus cinereus 1637 9834 11471 22.9Grey-tailed Tattler Heteroscelus brevipes 1947 8396 10343 25.9Ruddy Turnstone Arenaria interpres 893 893 0.9Great Knot Calidris tenuirostris 25325 69210 94535 24.9Red Knot Calidris canutus 2113 9952 12065 5.5Sanderling Calidris alba 1488 632 2120 9.6Red-necked Stint Calidris rufi collis 14051 19685 33736 10.5Curlew Sandpiper Calidris ferruginea 1804 4692 6496 3.6Grey Plover Pluvialis squatarola 542 681 1223 0.9Red-capped Plover Charadrius rufi capillus 2930 6052 8982 9.5Greater Sand Plover Charadrius leschenaultii 15131 28467 43597 43.6Oriental Plover Charadrius veredus 1032 49301 50333 71.9Gull-billed Tern Sterna nilotica 815 1877 2692 2.7Crested Tern Sterna bergii 617 617 -Roseate Tern Sterna dougallii 3226 3226 -Common Tern Sterna hirundo 2621 2621 -Little Tern Sterna albifrons 1306 1306 1.3Whiskered Tern Chlidonias hybridus 881 881 0.1White-winged Black TernChlidonias leucopterus727 1247 1974 -Table 8: Average counts of waterbirds at Roebuck Bay and Eighty Mile Beach(northern end only) Ramsar sites in 2004 / 2005 (Rogers et al., 2006c). Only the20 most numerically abundant species for each site are shown. The total countsfor the two sites are given, plus an estimate of the percentage of the East Asian-Australasian Flyway Population, based on official Wetlands International data(Wetlands International, 2006).
Coastal and Marine Natural Values of the Kimberley45.Most of these species are migrants thatmove twice a year to and from breedinglocations throughout Asia and as farnorth as Siberia. The dual availabilityof high quality estuarine feeding habitatand adjacent undisturbed roosts isessential to the viability of populations(Rogers et al., 2006a; Rogers et al.,2006b). Relatively small changes to theviability of either habitat can translateinto shifts in the distribution of birdsand an alteration of carrying capacity(Dolman & Sutherland, 1995).Arctic breeding waders such as GreatKnot, which are a key feature of theRoebuck Bay Ramsar site, stage theirmigration to replenish fat reserves inthe Yellow Sea before continuing their10,000 km flight to breed. In 2006,the completion of a sea wall acrossSaemangeum, at the mouth of theMangyeung and Dongjin Estuaries inSouth Korea meant the immediate andcatastrophic loss of the most importantstaging site in the Yellow Sea (Rogers &van de Kam, 2007). This loss has placedgreater demand on Australia to conservenorth west Australia’s shorebird habitat,since substantial decline in the ability ofbirds to reach migration fitness wouldhave a far greater cumulative impact ontheir ability to maintain this fitness tobreed in the Arctic.This emphasises the need and purpose forinternational agreements, to avoid a greaterthan necessary burden on any particularnation. Nevertheless, the ongoing loss ofstaging areas in central Asia representsan existing condition and one that, due toAustralia’s commitments under a rangeof migratory bird agreements, cannot beignored in managing the ecosystem ofnorth west Australia.6.10 BREEDING ISLANDSBreeding seabirds and turtle rookeries arean exceptional component of the region’scoastal ecosystem, which is relativelyundisturbed. Islands, such as Adele, theLacapedes, Booby Island, Low Rocks,Northeast and Northwest Twin Islands areof national or international significance.Seabirds are unable to breed unless thereis adequate access to feeding resourcesand many species have surprisinglylimited foraging ranges during criticaltimes of the year. Areas such as KingSound are likely to be critical foraginghabitat for Roseate Tern (George Swann,Kimberley Birdwatching pers. comm.),whilst tidal mixing zones with richecological productivity west of AdeleIsland (section 5.3.3) are responsible forthe viability of those seabird colonies.7. CONCLUSION6.11 RIVER MOUTHSAND CREEKSThe mouths of rivers and creeks provideimportant habitat for a range of speciesnot found elsewhere in the region. Theinfluence of the wet season is unknownbut at least one species, Little Tern,appears to depend on this as it is oneof the few seabirds that breeds in midsummer. Geomorphological featuresassociated with sediment, such assand banks, create the environment forseagrass to grow and provide habitatfor summer breeding birds such asLittle Tern. This species is widespreadthroughout the Kimberley but lesscommon in other parts of Australia and isexpected to associate with seagrass bedsand shallow sandy areas.Both Northern River Shark andFreshwater Sawfish are found in theseenvironments. The former specieshas not been seen in Queensland for20 years and the importance of theNorthern Kimberley, which has thelargest remaining populations of both,is put down to the relatively pristineenvironment (Thornburn & Morgan,2003; Thornburn et al., 2004).Biodiversity conservation is one of the pivotal principles of ecologicallysustainable development and is reflected through our laws and policies to protectspecies and their environment.International authorities under the Convention on Biological Diversity agree thatbiodiversity can only be managed from an ecological perspective. Provisionsfor management of the Commonwealth Marine Area and Ramsar sites, NationalOceans Policy, the Intergovernmental Agreement on the Environment andnumerous Western Australia state policies, reflect Australia’s progressivecommitment to ecologically sustainable development.This report provides an overview of some of the key elements of the Kimberleycoastal and marine ecosystem. Ultimately, it is hoped this will help responsibleauthorities, policy makers and the community identify potentially threateningprocesses and the detail and type of scientific knowledge marine ecologists can useto make a reasoned assessment of biodiversity value and impact significance.
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