2.4.12 Seabirds

Seabirds are key indicators of changing oceanographic and trophic conditions.481 They occupy upper-trophic levels of marine food webs and play a key role in the cycling of nutrients between marine and island ecosystems.481,482,483 

The Region supports breeding populations of 21 seabird species. All are protected under the EPBC Act.484 There are 55 key locations for nesting and roosting seabirds that are regionally and globally important. Most support multiple species of seabirds, and many (65 per cent) are in the Reef’s southern section.101 Overall, 39 of the 55 sites (71 per cent) are globally significant as they meet, individually or as a group, specific criteria, such as supporting greater than one per cent of the global population size of a species, over a season, and during one or more life history stages. The remaining 16 sites (29 per cent), which do not meet global significance criteria, are regionally significant as they support, for example, seabird species that are geographically restricted in their nesting area and/or one of the 5 largest nesting or roosting populations of seabird species in the Reef.101 Ten highly diverse seabird rookeries occur within the Reef, where populations of 7 or more species nest on islands and cays, including the most diverse, Raine Island (13 to 17 species).70,101 Notably, some seabird species, such as the Herald petrel, only nest in large numbers on a few of these key locations or exclusively on one.101

A photograph of an island covered in seabirds with smaller ones along the waterline and larger birds standing further back. In the background, multiple birds have taken flight.
Mixed species of seabirds on a coral island. © Andrew McDougall 2023*

Some species inhabit the Region year-round, while others migrate to distant foraging grounds where they remain for large parts of the year. As seabirds depend on resources both at sea and on land, they are exposed to impacts in both environments.485 Threats at sea include the depletion of prey resources driven by, for example, natural fluctuations in sea surface temperature, as well as environmental changes associated with climate change.481,486 Coastal and tourism development, the introduction of invasive animals and weeds and legacy impacts from land-based guano-mining continue to adversely affect seabirds on land.486 Erosion and overwashing of key habitats for nesting and roosting seabirds can be exacerbated by extreme weather events, sea-level rise and the destruction of vegetation.486

Improved demographic information is essential to understanding seabird condition 

Although seabird populations are an area of active investigation, current monitoring programs do not yet generate sufficiently robust demographic information, such as nesting success, that is essential to understanding the condition of seabird populations.70 High-quality baseline data for assessing longer-term condition and population trends remains limited to a few sites and species. Despite recent advances, knowledge about the distribution of pelagic foraging grounds also remains limited, mostly due to the small sample sizes of tracked birds from different colonies and species.487

Published in 2021, long-term trend analysis of populations of 9 seabird species from 32 of the Reef’s islands and cays found that trends varied markedly among species and sites from 1979 to 2018.486 Most species (including, for example, lesser and greater crested terns) showed increases and decreases at different sites. Overall, population declines were detected in 39 out of 86 assessed species and site combinations (45 per cent), followed by ‘no change’ in 31 (41 per cent) and increases in 12 combinations (14 per cent). Probable Reef-wide population declines occurred for 3 out of 5 assessed species, and no long-term changes were detected in the two most widely distributed species, including the brown booby. Declines of brown booby were offset by increases at a single large colony on East Fairfax Island, pointing to the likely success of habitat restoration on the island.

Overall, confidence in the condition (and trend in condition) of seabirds has improved since 2019 but remains limited. Although available information on population trends is highly site-specific, probable declines are occurring in some species, while other species’ populations appear static or have probable increases. Key pressures in the Region include climate-related environmental changes and impacts on availability of prey species.

*The copyright attribution has been updated on this website subsequent to tabling of the 2024 Great Barrier Reef Outlook Report.

  • 70. Richardson, L.S., Fuller R.A., Stewart D.A., McDonald J.A., Robertson K., Oswald S.A. 2023, Saving our seabirds: Variable breeding success of Red-tailed Tropicbirds in the Great Barrier Reef reveals the need for robust monitoring, Emu - Austral Ornithology 123(4): 345-356.
  • 101. Dutoit, J., Gray, S., McDougall, A., Armstrong B. 2023, Assessment of the protection and conservation management of important seabird nesting and roosting areas within the Great Barrier Reef World Heritage Area, Queensland Parks and Wildlife Service, Department of Environment and Science, Queensland Government.
  • 481. Congdon, B.C., Erwin, C.A., Peck, D.R., Baker, G.B., Double, M.C. and O'Neill, P. 2007, Vulnerability of seabirds on the Great Barrier Reef to climate change, in Climate change and the Great Barrier Reef: a vulnerability assessment The Great Barrier Reef Marine Park Authority, Townsville, pp. 428-467.
  • 482. Polis, G.A., Sánchez-Piñero, F., Stapp, P.T., Anderson, W.B. and Rose, M.D. 2004, Trophic flows from water to land: marine input affects food webs of islands and coastal ecosystems worldwide, in Food webs at the landscape level, eds G.A. Polis, M.E. Power and G.R. Huxel, University of Chicago Press, Chicago, Illinois, USA, pp. 200-216.
  • 483. Congdon, B.C., McDuie, F., Miller, M.G.R., Weeks, S.J. and Steinberg, C. 2014, Critical seabird foraging locations and trophic relationships for the Great Barrier Reef, final report to the National Environmental Research Program, Cairns.
  • 484. Commonwealth of Australia Declaration under s248 of the Environment Protection and Biodiversity Conservation Act 1999.
  • 485. Saraux, C., Sydeman, W.J., Piatt, J.F., Anker‐Nilssen, T., Hentati‐Sundberg, J., et al. 2021, Seabird‐induced natural mortality of forage fish varies with fish abundance: evidence from five ecosystems, Fish and Fisheries 22: 262-279.
  • 486. Woodworth, B.K., Fuller, R.A., Hemson, G., McDougall, A., Congdon, B.C., et al. 2021, Trends in seabird breeding populations across the Great Barrier Reef, Conservation Biology 35: 846-858.
  • 487. Miller, M., Hemson, G., Toit, J.D., et al. 2023, Refining seabird marine protected areas by predicting habitat inside foraging range - a case study from the global tropics, Preprint.