english not my motheltongue, solly...
...but I always thought a flock of horses, a flock of bisons (and in the 80s a flock of seagulls) but bees, locusts, birds, everything flying in a group is called a swarm. while blackbirds more or less live in couples. I was proven wrong.
but you are right, I rather have Tuis, Bellbirds or Fantails in my garden than blackbirds, starlings or sparrows