We don't have grackles here, Christine, and I haven't a clue if there is a name for a group of them! Be nice to learn, though, if anyone does know if there is one?
I think 'murder' is a good collective noun for crows, because as Melanie suggests, they are a bit sinister; and a 'clattering' is appropriate for jackdaws because that is exactly the noise they make! The one I like best is a 'parliament' of owls (I guess from the days when we thought politicians were wise!
)
'King Konky' is a wonderful name for a cat - do you have a photo?
And talking of wonderful names - Philip, is Glengarry the name of the place where you live? It's hugely evocative of green hills and stunning mountain views...
