What do you call a pair of ducks?

The answer depends upon whether they are in water or in flight:

In water, a group of ducks can be called a bunch, paddling, or raft.

In flight, a group of ducks can be called a skein, string, or team.

However, some terms were apparently coined by deviously creative minds (in a fit of passion, genius, or stupor, as with most manic spurts of creative zeal)-- thus, to be safe, I suggest using the term "flock of ducks".