His main role was the practice of augury, the interpretation of the will of the gods by studying events he observed within a predetermined sacred space (templum).
As circumstance did not always favour the convenient appearance of wild birds or weather phenomena, domesticated chickens kept for the purpose were sometimes released into the templum, where their behaviour, particularly how they fed, could be studied by the augur.
Augurs sought the divine will regarding any proposed course of action which might affect Rome's pax, fortuna, and salus (peace, good fortune, and well-being).
[2] Although ancient authors believed that the term "augur" contained the words avis and gerō – Latin for "directing the birds", historical-linguistic evidence points instead to the root augeō: "to increase, to prosper".
Magistracies included senior military and civil ranks, which were therefore religious offices in their own right, and magistrates were directly responsible for the pax, fortuna, and salus of Rome and everything that was Roman.
[3] The right of nuntiatio – announcing the appearance of auspicia oblativa (unexpected sign) – was reserved for the officiating augur, which would require the interruption of the proceedings then underway.
Membership gave the lifelong right to participate prominently in processions at ludi and in public banquets; augurs proudly displayed the symbol of the office, the lituus.
According to Cicero, the auctoritas of ius augurum included the right to adjourn and overturn the process of law: Consular election could be – and was – rendered invalid by inaugural error.
[12] Despite their lack of political influence under the Roman Empire, the augurate, as with its fellow quattuor amplissima collegia, continued to confer prestige on its members.
The role of the augur was that of consulting and interpreting the will of gods about some course of action such as accession of kings to the throne, of magistrates and major sacerdotes to their functions (inauguration) and all public enterprises.
[13] Since auguria publica and inaugurations of magistrates are strictly connected to political life this brought about the deterioration and abuses that condemned augury to progressive and irreversible debasement, stripping it of all religious value.
The templum, or sacred space within which the operation would take place had to be established and delimited (it should be square and have only one entrance)[23][24] and purified (effari, liberare).
[31] During the last centuries of the republic the auspices ex caelo and ex tripudiis supplanted other types, as the other forms could be easily used in a fraudulent way, i.e. bent to suit the desire of the asking person.
[32] Cicero condemned the fraudulent use and denounced the decline in the level of knowledge of the doctrine by the augurs of his time,[33] but in fact the abuse developed from the evasion of negative signs, described in the next subsection.
He divided the sky into four sections and observed birds: when they appeared he walked in that direction and found an extraordinary large grape that he offered to the gods.