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Location Australia, Queensland
Central coordinates 152o 4.50' East  23o 35.07' South
IBA criteria A4i, A4ii
Area 241 ha
Altitude 0 - 18m
Year of IBA assessment 2009

BirdLife Australia

Summary These small cays support over 1% of the world population of Wedge-tailed Shearwaters and Black Noddies, the majority of the populations of these species nesting off east Australia, and sometimes over 1% of the world population of Brown Booby.

Site description This IBA consists of the many small, low lying islands (~ 241 ha in total and between 2–18 metres high) comprising the Capricornia Cays of the southern inner Great Barrier Reef south of Rockhampton and Gladstone. The three largest islands, North West, Masthead and Heron, support the largest numbers of nesting Black Noddies in the Great Barrier Reef. The IBA also includes Tryon, Wilson, Wreck, West Hoskyn, Fairfax, Lady Musgrave and Lady Elliott Islands (other islands lack seabird data or have supported much smaller numbers of seabirds). Heron Island (16 ha), which supports an increasing and high density population of nesting Black Noddies, is half residential development, half National Park (29,349 breeding pairs of Black Noddy in 1982, 36,855 pairs in 1983 and 40,718 in 1985). Masthead Island (56 ha) is dominated by Pisonia grandis trees (20,000-24,500 pairs Wedge-tailed Shearwater in 1983-1985; 65,280 pairs of Black Noddy in 1983). North West Island is the second largest sand cay on the Great Barrier Reef (90 ha) and is forested with Pisonia grandis (271,710-288,000 pairs Wedge-tailed Shearwater in 1982-1985; 60,030 breeding pairs of Black Noddy in 1982 and 93,510 in 1983). Other significant islands include Tryon Island (10 ha cay with 16,000-26,000 burrows of Wedge-tailed Shearwater), Wilson Island (4.5 ha cay with tourist accommodation managed by Heron Island Pty Ltd; up to 500 nests Roseate Terns), Wreck Island (5.5 ha; 6500 pairs Wedge-tailed Shearwaters in 1982/3), West Hoskyn (1 ha; 15,000-26,000 pairs Black Noddy), Fairfax Islands (2-3 islands covering 19 ha; 7000-12,000 pairs Black Noddy; 1000-4000 pairs Brown Booby in 1984-1994 on Fairfax no.2), Lady Musgrave (4 ha; 11,000-16,000 burrows of Wedge-tailed Shearwater; 29,000-56,000 pairs Black Noddy), Lady Elliott (35 ha island with a tourist resort which is half forested with Casuarina equisetifolia; 3500 nests Crested Tern in 1985, thousands in 1986-1989). The region is sub-tropical, receiving an average 1062 mm rain anually(to 1989), average temperatures of 16-30 degrees and one tropical cyclone every two years. The whole area is in the Great Barrier Reef Marine Park; islands are variously in Preservation Zones (Wreck Island only), Conservation Park Zone or Habitat Protection Zone.

Key Biodiversity Other birds have not been documented for this IBA.

Non-bird biodiversity: North West has the second-largest Green Turtle colony in the world.

Populations of IBA trigger species

Species Season Period Population estimate Quality of estimate IBA Criteria IUCN Category
Wedge-tailed Shearwater Ardenna pacifica resident  1985-2002  560,000 nests  A4ii  Least Concern 
Brown Booby Sula leucogaster resident  1983-1990  1,000-4,000 nests  A4ii  Least Concern 
Black Noddy Anous minutus resident  1985-2002  300,000 nests  A4i  Least Concern 

IBA Monitoring

2008 high not assessed not assessed
Medium - based upon reliable but incomplete / partially representative data

Climate change and severe weather storms and floods likely in long term (beyond 4 years) whole area/population (>90%) moderate to rapid deterioration high
Human intrusions and disturbance recreational activities happening now some of area/population (10-49%) no or imperceptible deterioration low
Invasive & other problematic species, genes & diseases invasive non-native/alien species/diseases - named species happening now some of area/population (10-49%) moderate to rapid deterioration high

Protected areas

Protected area Designation Area (ha) Relationship with IBA Overlap with IBA (ha)  
Capricornia Cays National Park 180 protected area contained by site 178  
Capricornia Cays National Park (Scientific) 44 protected area overlaps with site 34  
Great Barrier Reef World Heritage Site 34,870,000 protected area contains site 241  


IUCN habitat Habitat detail Extent (% of site)
Coastline Sand cays, islets & bars  100%

Land ownership Australian Federal Government with management the responsibility of the Great Barrier Reef Marine Park Authority.

Land use

Land-use Extent (% of site)
nature conservation and research major
tourism/recreation major
Notes: Tourism developments on Heron and other islands

Protection status The IBA overlaps with Great Barrier Reef Marine Park, Mackay/Capricorn Marine Park and Capricornia Cays National Park (Scientific) and contains Capricornia Cays National Park.

References Dyer, P.K., O’Neill, P. and Hulsman, K. (2005) Breeding numbers and population trends of Wedge-tailed Shearwater (Puffinus pacificus) and Black Noddy (Anous minutus) in the Capricornia Cays, southern Great Barrier Reef. Emu 105: 249-257.

GBRMPA (1997) Guidelines for Managing Visitation to Seabird Breeding Islands. Great Barrier Reef Marine Park Authority unpublished report.

Hill, G.J.E., Carter, J.L., Barhnes, A., Dyer, P.K. and Rosier, D.J. (1997) The Black Noddy breeding population at Heron Island, Great Barrier Reef: 1985-1989. Corella 21: 58-64.

Hulsman, K., Walker, T.A. and Domm, S. (1993) Tryon Island, Great Barrier Reef, Queensland. Corella 17: 152-154.

Hulsman, K. and Walker, T.A. (1996) North West Island, Great Barrier Reef, Queensland. Corella 20: 107-110.

Hulsman, K., Walker, T.A. and Limpus, C.J. (1999) Wreck Island, Great Barrier Reef, Queensland. Corella 23: 88-90.

Jahnke, B.R. (1977) Masthead Island, Queensland. Corella 1: 48-50.

O’Neill, P. Olds, J. & Elder, R. (1997) Report on investigations of Pulvinaria urbicola infestations of Pisonia grandis forests, and masked and brown booby populations in the Coral Sea. 25 November to 18 December 1997. Environment Australia Report.

Walker, T.A. (1985) Crested Terns Sterna bergii on southern Great Barrier Reef islands 1985-1986. Corella 12: 53-56.

Queensland Parks and Wildlife Service (2007) GBR Seabird Database (accessed May 2007).

Walker, T.A. (1989) Lady Elliot Island, Great Barrier Reef, Queensland. Corella 13: 118-121.

Walker, T.A. and Hulsman, K. (1993) Wilson Island, Great Barrier Reef, Queensland. Corella 17: 155-157.

Walker, T.A., Hulsman, K. and Domm, S. (1993) Fairfax Islands, Great Barrier Reef, Queensland. Corella 17: 159-161.

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Recommended citation  BirdLife International (2016) Important Bird and Biodiversity Area factsheet: Capricornia Cays. Downloaded from on 24/10/2016

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