Stephanie Morren from the RSPB writes…
What do we know about the effect of disease on turtle doves? Well the answer is, not a lot at the moment. We know a little about other potential problems facing turtle doves on their breeding grounds in Europe, their wintering grounds in Africa and their migration routes. But could disease be an additional problem for this fast-declining bird?
Rosie Lennon, Jennifer Stockdale, Simon Goodman and Keith Hamer from the University of Leeds, along with Jenny Dunn and Tony Morris from the RSPB, recently had an article published in the journal Parasitology about this very subject. The link to the abstract, and the journal can be found here. But below is a summary of what they found out.
Trichomoniasis is a disease commonly found in doves and pigeons (or Columbidae) caused by the Trichomonas parasite. It is known to be a problem for the endangered Mauritius pink pigeon for example, where it can result in high mortality in young pigeons in the nest. It has recently been found in greenfinches, passed on via infected garden bird feeders, and led to a 35% decline in greenfinch numbers within a year in the UK.
This study aimed to establish whether the disease was present in wild turtle doves, as well as in three other similar species – collared doves, woodpigeons and stock doves. It also aimed to understand the disease better and find out whether the disease found in doves and pigeons is the same strain killing greenfinch.
The team found the parasite present in all four species, but turtle doves and collared doves were the most likely to carry the parasite with 86% being infected. This was the first time that the parasite has been confirmed in turtle doves in the UK. Unlike the other Columbidae studied, turtle doves rely on seed food all year and they are a migratory species. Increased agricultural efficiency has reduced the availability of arable weed seeds during the period when turtle doves migrate back to Europe from Africa and it is possible that this food stress makes them more susceptible to disease. On farms where supplementary food was put out for game birds, more of the doves and pigeons were found to have the parasite. This suggests that in a similar way to the disease being passed between greenfinches on garden feeders, it can be passed between wild birds on farms in this way. This is likely to be due to a food source, whether supplementary feeding or accidental spillages, attracting a lot of birds to the same place meaning it is easier for the parasite to pass between birds. Of the birds that were shown to have the parasite, hardly any were showing clinical signs of the disease such as saliva round the beak, so it is unclear what effect, if any, this parasite is actually having on these birds.
Four strains of this parasite were identified, but more work is needed to find out whether any of these are identical to the strain killing greenfinches. Overall, as well as providing the first evidence of the extent of infection in turtle doves in the UK, this work also highlights the need to understand the effects and implications of Trichomonas parasites on the host bird.