Don’t kill birds with kindness

With my son starting to show an interest in feeding our garden birds, I was interested to read two reports this month reminding us to do so with care.

Researchers from the Scottish Agricultural College have highlighted the fact that Salmonella can build up on feeders or drinkers, with the potential to kill birds already vulnerable after a hard winter. [See: Kindness Can Kill – Bird Lovers Urged To Clean Up At Feeding Time].

In a paper published in The Veterinary Record1, Tom Pennycott and colleagues describe the findings from 198 incidents of salmonellosis in garden birds in Scotland between 1995 and 2008. In the north of Scotland finches, especially greenfinches, were most commonly involved, but in the south of Scotland Salmonella infection was also a problem in house sparrows.

The researchers say that bird lovers should clean and disinfect feeders and feeding stations regularly and allow them to dry before using them again (also remember to wash your hands well after handling as some bird Salmonella strains can infect humans). By using several feeding sites, people can reduce bird numbers in any one place and moving the feeding sites regularly can reduce any build-up of debris and infectious agents around the feeders. Occasional rest periods will help to reduce levels of contamination.

Searching the Abstracts on VetMed Resource, I note that an earlier paper by Pennycott and colleagues found that salmonellosis was a common cause of death in greenfinches, house sparrows and chaffinches, and was also responsible for the deaths of other birds such as goldfinches, feral pigeons and different species of gulls2.

However Salmonella is not the only challenge facing our garden birds. An article in New Scientist3 highlights the fact that bird feeders have also played a key role in transmitting two diseases among songbirds, mainly finches, in Europe and North America. The first of these diseases is conjunctivitis caused by Mycoplasma gallisepticum. The bacterium has apparently killed 60 per cent of house finches in the eastern USA. An interesting abstract on VetMed Resource describes an experiment demonstrating that birds can pick up M. gallisepticum from making contact with feeders4. In Europe, another feeder-related disease is trichomoniasis caused by the parasite Trichomonas5,6. It causes throat swelling, causing birds to starve, and has reportedly killed about a fifth of the UK's greenfinches.

Next month, experts are gathering at an international meeting in London to discuss the feeding and management of garden birds. The symposium, 'Wild bird care in the garden' will address nutritional aspects, effects on breeding and survival, and technological advances as well as epidemiology of diseases.

According to the RSPB, over half of adults in the UK feed birds in their garden. For their advice on how to do this with care, see: Hygiene – vital precautions.

References

1. Salmonellosis in garden birds in Scotland, 1995 to 2008: geographic region, Salmonella enterica phage type and bird species. Pennycott, T. W.; Mather, H. A.; Bennett, G.; Foster, G. Veterinary Record 2010, Vol. 166, No. 14, pp.419-421

2. Isolation of different serovars of Salmonella enterica from wild birds in Great Britain between 1995 and 2003. Pennycott, T. W.; Park, A.; Mather, H. A. Veterinary Record 2006 Vol. 158 No. 24 pp. 817-820

3. Garden bird feeders spread diseases by Andy Coghlan. New Scientist, 13 April 2010.

4. Experimental evidence for transmission of Mycoplasma gallisepticum in house finches by fomites. Dhondt, A. A.; Dhondt, K. V.; Hawley, D. M.; Jennelle, C. S. Avian Pathology 2007 Vol. 36 No. 3 pp. 205-208

5. Increase in trichomonosis in finches. Simpson, V.; Molenaar, F. Veterinary Record 2006 pp. 606

6. Epidemic mortality in greenfinches at feeder stations caused by Trichomonas gallinae – a recent problem in Northern Germany. Peters, M.; Kilwinski, J.; Reckling, D.; Henning, K. Kleintierpraxis 2009 Vol. 54 No. 8 pp. 433-438

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