I think the meanings of these words are changing. The original question was
whether an author, who is not a birder, should use one word or the other in
a story. The answer may depend on the time and location in which the story
is set.
I offer the definitions of these words found in: "A Crash of Rhinoceroses; A
Dictionary of Collective Nouns," by Rex Collings. He cites Henry Coleman
Folkard, in "The Wild Fowler" (1859): "There cannot be stronger proof [of]
the ignorance of the present age, as regards the original act of
wild-fowling, than by reference to the erroneous terms which are applied to
the pursuit by nearly all modern sportsmen; and it is only from the lips of
a few 'ancient -fowlers', however illiterate that we hear the correct
version of sporting terms applicable to wild-fowling... To speak in the
present day of a 'flock' of partridges instead of a 'covey', would so
offend the ears of the most superficial sportsman, that he would look upon
an individual who made use of such a term with profound pity at his
ignorance; and yet the term 'flock' as applied to wild-fowl is equally
erroneous, and quite as inexcusable, when coming from the lips of a
sportsman... Writers upon sporting literature, one and all, commit similar
errors... Let us hope the character of the English sportsman is not so
degenerated, or the respect he owes to ancient diversions so far forgotten,
as to permit him any longer to persist in such cramped and improper slang as
to use the inapplicable term 'flock' to every or any description of any
wild-fowl..."
He implies that 'flock' should be applied only to sheep, as in The Gospel
according to St. Luke: "And there were in the same country shepherds
abiding in the fields, keeping watch over their flocks by night."
The Dictionary of Collective Nouns has the following notes under "A Raft of
Waterfowl: Craigie and Hubert describe raft as a dense flock. Lawson's
'Carolina' (1709): 'Raft fowl includes all the sort of small ducks and teal
that go in rafts along the shoar.'"
Bill Applegate
applgate at whidbey.net