Like others said,
document what you can, on paper & by media (vid, photos etc.).
Hand all evidences to appropriate authorities (AC, ASPCA etc.).
You can also scare them by saying you will approach health department if they do not do anything for it because you suspect that it may have the possibility to spread bird viruses (very contagious to humans like i.e. bird flu) just because they (the store) cannot prove that it had already taken that sick bird to a vet to verify.
Something serious like "bird flu" will sure get heath department into a store pronto!
P.S. You never know where they get their "doves" from... maybe even China (they eat doves there & is mass produced; who knows... maybe pet stores are getting them from there cheap?) where there is a case of a confirmed case of "Bird Flu" that happens only just this month! (that of a
16 year old & also the
27 year old) That is 3 cases already in just the beginning of 2009 on this month of January.
Plus P.S.
If AC or ASPCA cannot get a store to close, heath department can actually officially close stores down if there is potential heath threats to humans... they will be forced to close!