Not So Great Expectations

It appears that a virus, Avian pox is decimating many small bird populations, including that of the Great tit (Parus major) in the UK (http://www.guardian.co.uk/environment/2011/aug/03/garden-birds-avian-pox-virus?INTCMP=SRCH ). It is, apparently, difficult to see precise effects of the virus but it impairs both flight and vision. Concentrating the birds at feeding centres could facilitate transmission of the infective agent.