Joseph Greenberg's short The Influence of Islam on a Sudanese Religion is an interesting account of the "pagan" religion of Hausa in the Kano area. Although dated and perhaps incorrect about the particulars of early Hausa history and Islamic conversion (influences from Kanem-Borno appear to be important, not just Islamic influences from Mali or the Fulani), Greenberg traces the relationship between Islamic/Mohammedan religion and the local, "pagan" bori and iskoki worship of the Maguzawa Hausa. Through centuries of living alongside Muslims or being in interaction with Muslims (initially said to be West African Muslims influenced by Maghrebi Islamic practices), the children of bori have absorbed elements of Islam and even created a new spirit based on their knowledge of the faith. Nonetheless, two religious traditions are distinct and reflect the ways in which West African religions have coexisted and adapted elements from Islam into their own local settings.
In this regard, Hausa "traditional" religion brings to mind traditions like Haitian Vodou, where interaction with a monotheistic religion has led to some acculturative results while not diminishing the importance of the spirits. Even Hausa Muslims, like non-Vodouisant Haitians, often believe in the power of the spirits. As devotees of their respective Abrahamic faiths, however, they see "serving the spirits" as unlawful or wrong. But continued belief in the efficacy of these spirits for healing and other purposes must play a role in the survival of Vodou and Maguzawa religion. Furthermore, like Haitians, the Maguzawa believe Allah is a distant, remote Creator and focus on sacrifices to spirits for help. Like the Catholic saints sometimes identified with spirits, the Hausa associate jinn, including those of Islamic origins, with the iskoki and have adopted a dichotomy of "black" and "white" spirits based on the urban vs. rural, Muslim vs. pagan factors in their history. Last but certainly not least, the domestic, rural practices of the cult are rooted in patrilineal sibs among the Hausa in which the male head of the extended family is often in charge of the rites. Spirit possession rituals, tied with specific drum rhythms and instruments, are also important in the bori possession cult (linked to healing), like that of Haitian Vodou.
Even more intriguing is to see the similarities of Hausa traditional religion with other parts of West Africa. The belief in a serpent-rainbow deity, Gajimari, for instance, and the known historical and cultural contact between the Hausa and other peoples like the Yoruba, may hint at ancient influences. The past importance of the Kutumbawa Kano kings in pre-Islamic rituals, including sacrifices that allegedly included humans, also brings to mind some other West African kingdoms. Even the Hausa word used for a "pagan" medicine man who consults the spirits to cure patients, sounds a little like the bocor or bokono of the Yoruba and Benin areas. While some of the iskoki included in Greenberg's table may differ from Hausa descriptions of the spirits outside of the Kano region, it seems likely that the Hausa iskoki spirits are generally similar and indicate a belief in spirits as the cause and cure for various ailments. Moreover, the Hausa seem to believe the iskoki reside in a city to the east, Jangare, with a political administration similar to the Hausa kingdoms. Hausa "paganism" is undoubtedly related to those of other West African peoples and, perhaps, one of the contributing traditions to Haitian Vodou.