Birds serve throughout the entire Celtic tradition as symbols of divinity and as messengers and servants of the gods. There was a Celtic belief in malevolent otherworld flocks of birds, which came to bring harm and destruction to villagers in closely regulated season, usually Samhain. The druids used birds as a form of prognosis, the raven was one of great importance. The druids in Gaul fore told the future by observing the flight of certain birds and in Ireland the raven and wren were much used in augury. In Celtic folkore and mythology, birds are heavily associated with death and transformation. Many significant figures were said to not have died, but rather have been transformed into various bords. Some examples of this can be seen below:

Blodewed          Owl
Children of Lir   Swans
Eliwlod           Eagle
King Arthur       Raven
Llew Llawgyffes   Eagle

There is an ancient Celtic belief that the soul leaves the body like a bird dlying out of the man or woman dying. Within Cornish traditions, departed souls are belived to be `pisky,’ which is a term used for both the fairies and the moths.

Night flying birds, or birds with dark feathers or an eerie cry, are mostly though to be ill omens. The mournful cries of a flock of birds called the Seven Whistlers – they may have been curlews, whimbrels or plovers – were believed to warn of an impending death or disaster. In Shropshire and Worcestershire, there were said to be six whistlers searching for the seventh; if they found it the world would end. In other places the Seven Whistlers were the grief stricken souls of unbaptised children condemned to roam the skies forever, or drowned sailors warning their former shipmates of danger.
Birds are usually used to represent prophetic knowledge, (Davidson, 91) bloodshed, and skill. In an omen, birds can be either the message or the messenger. For example, MorrĂ­gan came in the shape of a bird to warn the Brown Bull (Kinsella, 98). The interpretation of their calls and movements
can lead to knowledge of future events. Birds, especially ravens and crows, usually presage bloodshed and battle, when they are associated with it,
sticking with the theme of prophesy. Deirdre’s dream of three birds drawing blood foreshadowed death and Lleu Llaw Gyffes was shedding rotting flesh
and maggots while in the form of an eagle. The Irish war goddesses were said to call the ravens down to battle fields to feast on the flesh of the
slain (Davidson, 98). Even normal, modern crows and ravens descend to feed on corpses along the road.

Birds can also be used to demonstrate a warrior’s prowess by their method of capture. Lleu Llaw Gyffes was so skilled he could hit birds with a stone
without killing them outright (Ford, 101). CĂșchulainn demonstrated even more prowess capturing birds skillfully, but his son, Connla was still more skilled. He could not only stun them with a stone, but also with only his voice (Kinsella, 39, 91).