Congdon et. al., 2007:

"Most previous studies document the impact of climate on seabirds as seasonal or longer term correlations between reproductive demographics and large-scale oceanographic processes, such as the El Niño-Southern Oscillation (ENSO). Specifically, this work suggests that ENSO type phenomena impact important demographic parameters, such as the timing of breeding, year-to-year recruitment, number of breeding pairs and hatching success on an annual or longer-term basis. Both beneficial and detrimental seasonal or longer-term impacts have been observed in a number of temperate ecosystems, but to date only detrimental effects have been documented in tropical ecosystems.

As well as these larger-scale longer-term impacts, there is also recent evidence that sea temperature variation at smaller within-season and day-to-day time scales significantly impacts seabird foraging success, growth patterns and reproductive output, regardless of prevailing ENSO type conditions. While not totally independent these longer and shorter-term processes may operate on different reproductive parameters and involved substantially different trophic interactions. Therefore, documented impacts at each of these scales will be examined separately, along with available evidence of the possible trophic mechanisms responsible for each.

Large-scale ENSO processes have also been associated with negative impacts on tropical seabird breeding success in the Coral Sea and along the north-east Australian coastline, especially for colonies on or adjacent to the Great Barrier Reef. Such impacts have been particularly obvious during events like the 1997 and 1998 ENSO. Extremely high sea surface temperature increases during this event were also accompanied by severe reef-wide coral bleaching.

Current population data at Raine Island in the far northern Great Barrier Reef indicate a potential progressive decline in breeding populations of at least 10 of the 14 breeding species. This negative trend is consistent across all species with relatively large breeding populations. Declining species listed in descending order of reduction are: common noddy (95.5%), sooty tern (84.4%), bridled tern (Sterna anaethetus) (69.1%), red-footed booby (67.9%), least frigatebird (67.6%), brown booby (40.4%), red-tailed tropicbird (38.5%), masked booby (26.9%) and wedge-tailed shearwater (18.6%).

Eighteen years of data from Michaelmas Cay in the northern Great Barrier Reef also show significant relationships between population trends and ENSO climatic indices at multiple levels (Erwin et al. unpublished data). Of primary importance is that breeding populations of the two pelagic foraging species, the sooty tern and common noddy, showed significant negative correlations with ENSO intensity in the year following each breeding survey. Similar relationships were not found for the inshore foraging crested tern that is thought to supplement natural food sources with discards from trawlers.

Long-term data on seabird abundance and demography from the Swains Reefs in the southern region of the Great Barrier Reef show negative population trends for brown boobies in both the number of active nests and total adults on all but one of seven islands studied. The causes of these significant declines are unclear, but the authors believe that they are unlikely to be human disturbance induced.

Wedge-tailed shearwaters and black noddies numerically dominate breeding seabird species of the Capricorn Island group in the southern Great Barrier Reef. The black noddy population on Heron Island has increased exponentially since early last century, however, recent censuses on Heron Island demonstrated a substantial decrease in active nests from approximately 70,000 to 30,000 between 1996 and 2000. Mass mortality of both adults and chicks was observed in January 1998 coinciding with the 1998 ENSO event and extensive coral bleaching in the region."

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Citation and/or URL

Congdon, B.C., Erwin, C.A., Peck, D.R., Baker, B.G., Double, M.C. & 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, eds. J.E. Johnson & P.A. Marshall, Great Barrier Reef Marine Park Authority and Australian Greenhouse Office, Townsville, Qld, 427-463.. 

Spatial Coverage

 Great Barrier Reef World Heritage Area

Temporal Coverage

 >30 years

Update Frequency

Information current as of 2007

Other Information

 None