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Waterbirds are showing widespread declines, particularly in Asia

Red Knot, © Jan van de Kam

Populations of waterbirds throughout the world are suffering declines and Asia is particularly seriously affected. Analyses at the global, regional, country, taxonomic group or species level all indicate that populations of many previously common waterbird species are decreasing.


Waterbird population trends in different regions

Analysis confined to those waterbird populations where trend information is available. Delany and Scott (2006).

Waterbirds are a diverse group of over 30 families which are characteristic of, and ecologically dependent on wetland habitats. Many waterbird species are highly visible, often occurring in spectacular concentrations. Wetland ecosystems support a wide variety of biodiversity and throughout the world, human livelihoods depend upon their condition. Waterbirds represent one of the most obvious indicators of the health and diversity of such ecosystems.

Many waterbird species are declining with 17% of waterbird species considered globally threatened (BirdLife International 2008). In 2006, an analysis found that overall 40% of the 1,200 waterbird populations for which trends were known were in decline, with only 17% increasing (Delany and Scott 2006). Reliable trend data are unavailable for 48% of the world’s 2,305 waterbird populations and the availability of information varies between regions. Data from a well-studied region such as Europe (where estimates are available for 73% of 351 populations) showed a similarly high proportion (41%) of populations in decline. Although Asia is a very important region for waterbirds, trend information is available for relatively fewer populations (44% of 815 populations), but of these, 59% are declining (Delany and Scott 2006).  

At the country level, long-term studies are also reporting alarming waterbird declines. For example, a recent review of long-term trends of shorebird populations in eastern Australia reports that migratory populations have plummeted by 79% over a 24-year period (Nebel et al. 2008).

Trends for specific waterbird families also paint a negative picture. For one of the better-known groups of waterbirds, the Anatidae (ducks, geese and swans), trend estimates are available for 75% of populations. Of the 468 populations identified for the 164 species in the family, 4% are considered extinct and a further 38% are declining; fewer populations (19%) appear to be increasing (Delany and Scott 2006).

Many previously common migratory waterbird species are undergoing dramatic declines in parts of their ranges. The Red Knot Calidris canutus rufa subspecies which migrates annually between the Canadian Arctic and Tierra del Fuego has undergone a drastic recent decline, from 100,000 individuals in 1989 to just 17,200 in 2006. Although the causes are not yet fully understood, the decline is mainly attributed to human harvesting of key food sources reducing food availability at important stop-over sites (Baker et al. 2004).



Related Case Studies in other sections

Related Species

References

Baker, A. J., Gonzalez, P. M., Piersma, T., Niles, L. J., deLima Serraro do Nascimento, I., Atkinson, P. W., Clark, N. A., Minton, C. D. T., Peck, M. K. and Aarts, G. (2004) Rapid population decline in Red Knots: fitness consequences of decreased refuelling rates and late arrival in Delaware Bay. Proc. R. Soc. Lond. B. 271: 875–882.
 
BirdLife International (2008) Threatened birds of the world. CD-ROM. Cambridge, UK: BirdLife International.
 
Delany, S. and Scott, D. (2006) Waterbird Population Estimates. Fourth Edition. Wageningen: Wetlands International.
 
Nebel, S., Porter, J. L. and Kingsford, R. T. (2008) Long-term trends of shorebird populations in eastern Australia and impacts of freshwater extraction. Biol. Conserv. 141: 971–980.

Compiled 2004, updated 2008

Recommended Citation:
BirdLife International (2008) Waterbirds are showing widespread declines, particularly in Asia. Presented as part of the BirdLife State of the world's birds website. Available from: http://birdlife.org/datazone/sowb/casestudy/71. Checked: 22/08/2014