Ibis ecotoxicology

Contaminants in eggs of Australian white ibis (Threskiornis molucca) from urban through to inland sites

This project examined how contaminant levels in eggs of the Australian white ibis (Threskiornis molucca) differed across sites from three different location categories with differing degrees of urbanisation: urban, peri-urban and inland. A total of 219 eggs from 11 colonies were sampled for egg traits (egg weight, volume, content, width, length and shell weight and thickness). Of these, 34 eggs were analysed for their contaminant concentrations.

Project timeframe 

July 2010 – July 2011


Our principal objective was to examine whether selected POPs (dioxinsPCDDs, furansPCDFs, PCBs, PBDEs and OC pesticides) varied in concentration in the eggs of Australian White Ibis (Threskiornis molucca) collected from urban, peri-urban and inland sites. We predicted that increased exposure in urban areas would be reflected in contamination profiles. We also measured egg traits in different regions to determine if there were differences related to exposure to contaminants.

Project outputs, outcomes and impacts

Certain contaminant groups such as polychlorinated dibenzo-p-dioxins, polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs), were detected at between seven and nine times higher concentrations at urban sites compared to inland sites and were also significantly greater than at peri-urban sites. High urban contaminant levels were attributed to exposure to contaminants in highly populated areas, potentially occurring when parental birds foraged in landfill sites or in industrial areas.

In contrast, concentrations from polychlorinated dibenzofurans, an urban and industrially associated contaminant, were significantly higher at inland sites compared to urban and approximately four times higher than at peri-urban sites. Furan data from the inland Macquarie Marshes site included one egg with markedly elevated furan levels, which may be potentially linked to manufacturing by-products of pesticides and fungicides.

There was large variation in total DDT concentration, an ubiquitous pesticide group, with no clear difference between site categories. This may be attributed to extensive DDT use across the country from agricultural practices until the late 1980’s.

Patterns in egg traits (egg weight, volume, content, width and shell weight) also reflected the location of colonies; traits were significantly reduced at the majority of urban sites, compared to peri-urban and inland sites. Factors such as smaller sized eggs have been associated with reduced chick survival and therefore urban bird colonies may experience a risk of lower breeding success. In comparison to toxicological data for other birds studied around the world, most contaminant levels in Australian white ibis eggs are relatively low, but there is clear evidence of contamination related to proximity to urban areas.


Ridoutt, C. V. L. and Kingsford, R. T. (2011). Organohalogenated pollutants in Australian white ibis (Threskiornis molucca) eggs. Report by the Australian Wetlands and Rivers Centre, University of New South Wales, Sydney  Click here for report

Collaborators, partners and sponsors

Analytical laboratory work and High Resolution Mass Spectrometry carried out at the Dioxin Analysis Unit, National Measurement Institute, Pymble, NSW.

Research Program: 
Research Themes: 
Rivers and Wetlands

Publications for this project

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