At the end of December 2014 a resident of the Dutch town of Heerlen reported finding a number of dead sparrows in her garden and that the remaining sparrows appeared weak. One of the sparrows in an early stage of decomposition was submitted for post-mortem investigation at the Dutch Wildlife Health Centre (DWHC); this showed the cause of death to be an infection of the crop with Salmonella groep B bacteria.
Since 2010 Salmonella has been identified as the cause of death in 10 sparrows and 2 green finches submitted to the DWHC in the winter months (November to March).
In the light of these findings it is important to understand why sparrows are susceptible to this bacteria whilst, tits for example, are not; and, how the spread of infection can be prevented. The following information is from the British Trust for Ornithology:
Many different sorts of Salmonella bacteria can infect and cause disease in a range of species; in garden birds salmonellosis is caused by Salmonella typhimurium. In wild birds the disease tends to be seen during winter months particularly amongst seed-eaters that live in groups such as house sparrows and green finches.
Salmonella bacteria can survive for some time in the environment. The bacteria are probably passed between birds via feces in shared areas such as feeders or bird baths. Regular cleaning of these sites is particularly important because Salmonella typhimurium can also cause disease in humans and pets.
If you put food out for birds in your garden then follow this advice to minimise the risk of creating a source of Salmonella infection.