From publisher blurb:
The animals of the forest come in all shapes and sizes, natural and unnatural. Wolves, foxes and bears are common, but perhaps the most ubiquitous are birds of all varieties. Probably the most noticeable of these are the various forms of the crow family that haunt the eaves of the forest and fly high above. Crows, rooks, ravens and magpies are often encountered, and now that no aeroplanes take to the skies the birds have that entire domain to themselves.
To the Drifters and communities that exist beneath the canopy, birds are a constant companion to their lives. Their calls echo through the woods, and the dawn chorus can be deafening. At twilight, the birds roost high in the many trees, but not before they soar over tree tops in aerial displays.
But of course in the Sea of Leaves natural creatures are accompanied by their unnatural counterparts – those that act in ways subtly different to their manner before the event. Unnatural birds come in as many forms as their normal brethren, but crows seem to be the most common form. These creatures are another expression of the strangeness of the forest, watchful eyes that cannot be escaped.
A murder is the collective name for a group of crows, but in the post-Event world it is the name people use to describe any unnatural form of birds that they may encounter the forest.