Though their organization is invisible to most outsiders, who consider druids to be loners, druids are actually part of a society that spans the land, ignoring political borders. A prospective druid is inducted into this society through secret rituals involving tests that not all survive. Only after achieving some level of competence is the druid allowed to strike out on her own.
All druids are nominally members of this druidic society, though some individuals are so isolated that they have never seen any high-ranking members of the society or participated in duidic gatherings. All druids recognize each other as brothers and sisters. Like true creatures of the wilderness, however, druids sometimes compete with or even prey on each other.
A druid may be expected to perform services for higher-ranking druids, though proper payment is tendered for such assignments. Likewise, a lower-ranking druid may appeal for aid from her higher-ranking comrades in exchange for a fair price in coin or service.
Obviously we're not required to enforce the rules as written, but let's assume that we want to. :) We know that Arlindil "liaises between the Winter Council and Golarion's elven druids . . ." (A Memory of Darkness, p. 24), so clearly the two secret societies are prepared for some give and take. Presumably Arlindil had some operatives answering to him who were also members of this society.
There's nothing saying that drow can't be druids, so that's likely an example of preying on each other (as described above). I don't know if this is a situation where Winter Council druids or drow druids could be forced into helping each other (or even sparing each other), but it seems worth pondering.
Is this also a way that the Winter Council might have employed non-elf operatives in the past? If some WC druids are working to foil a drow plot and some non-elf druids are nearby and of lower rank, they seem obvious recruits. As a secret society, druids must be used to keeping secrets.
I'm not really sure where I'm going with this, but it's amusing me to turn it over in my brain.
Ooo - thanks for bringing this up. I hadn't really considered that angle. I'm just wrapping up Shadows in the Sky (with a tie-in to Burnt Offerings), and had introduced a conspiracy of young Druids (a mix of pcs & npcs) investigating the Blot and people shown to them in visions tied into events relating to it (aka the PCs). If there are Druids involved with the Winter Counsel, this gives me another whole hook to snag my group into the later scenarios (mine is a fractious and varied lot, and sometimes need more than one excuse to drag them into a storyline).
As a society, I've never seen Druids as much for hierarchy or organization - more like the colored Wizards in Tolkeen's Middle Earth (ala Gandalf the Gray and Sauruman the White), a rugged associations of equals (though some more equal than others), each doing their own thing, but capable of being a frightening force when they band together.