Mixed feeding groups

Interesting question

I would have liked more time to check the literature, but instead here is a
personal view.

In the coastal forests of eastern South Africa the Square-tailed Drongo
(Dicrurus ludwigii) leads bird parties. They are early risers and seem to
call until they attract a regular set of species. Dark-backed Weaver and
Terrestrial Brownbul are almost always there. Then the party moves slowly
through the forest. The Drongos are very sharp and quickly spot and
fiercely mob small accipiters that might appear. In return they seem to be
after any flying insects disturbed by gleaners. This is more often observed
in winter than summer.

Fork-tailed Drongo probably plays a similar role in woodlands.

Not sure if this is published.

Regards
Richard Boon