Roman-era and migration-period archaeological sites. The most detailed description of Germanic lots is found in Tacitus, Germania, chapter 10. According to Tacitus, the Germani cast lots, made from the wood of fruit-bearing trees and marked with signs, onto a white sheet, after which three lots were drawn by either the head of the family or a priest. While the signs Tacitus mentions have been interpreted as Runes, most scholars believe they were simple symbols. Thirteenth-century Icelandic sources also attest the drawing of lots carved with signs; however, there is debate about whether these late sources represent a form of ordeal that was introduced with Christianity or a continuation of Germanic practice. Another important form of divination involved animals. The interpretation of the actions of birds is a common practice across the world and is well attested for the Germani and the Norse. More uniquely, Tacitus says the Germani used the whinnying of horses to divine the future. Although there is no later or corroborating evidence for Tacitus's horse-divination, the importance of horses in Germanic religion is well-attested. Both forms of divination might be connected to the portrayal of birds and horses on gold bracteates. A few other methods of divination are also attested. Tacitus mentions duels as a method of learning the future; while Norse sources attest many duels, none are obviously used for divination. Roman and Christian sources sometimes claimed that the Germanic peoples used the blood or entrails of human sacrifices to divine the future. This may derive from ancient topoi rather than reality, although blood played an important role in pagan ritual. Norse sources include additional forms of divination such as a form of necromancy known as , as well as seiðr rituals. Feasts and festivals The evidence suggests that the Germanic peoples had recurrent sacrifices and festivals at certain times of year. Often these feasts involved sacrifice at communal meals, ritual drinking, as well as processions and divination. Almost all information on Germanic religious festivals concerns Western Scandinavia, but Tacitus mentions a sacrifice to the goddess Tamfana took place in the autumn, while Bede mentions a festival called Mōdraniht that occurred in early February, and Jonas of Bobbio's Life of Saint Columbanus (640s) mentions a festival to Vodan (Odin) held by the Suebi that involved the drinking of beer. On the basis of several informants and possibly textual sources, Adam of Bremen describes a Swedish sacrificial