Tweetie birds die by the MILLIONS all the time, everywhere...
The most recent figures are from the Mammal Society, which estimates that the UKs cats catch up to 275 million prey items a year, of which 55 million are birds. This is the number of prey items that were known to have been caught we dont know how many more the cats caught, but didnt bring home, or how many escaped but subsequently died.
The most frequently caught birds, according to the Mammal Society, are probably (in order) house sparrows, blue tits, blackbirds and starlings.
Despite the large numbers of birds killed, there is no scientific evidence that predation by cats in gardens is having any impact on bird populations UK wide.
http://www.rspb.org.uk/gardens/advice/cats/Copy_of_index.asp
What kills most birds is chemicals and urban sprawl....not a cat.