The BBC reports (amongst others) that a disease is being spread amongst birds at feeders and is impacting Greenfinch and Chaffinch populations. Greenfinches are down 35% in some areas apparently and advice is to keep your feeders and bird baths clean to minimise communication of the disease.

One theory is that Greenfinches in particular are affected because of their tendency to crowd feeders in groups, hence spreading the disease. The picture above demonstrates that tendency nicely, complete with mid-air queuing.