Thanks for the link. Others may also be interested in the communications with Arkansas and the newly formed Confederacy prior to this declaration -- all of which are in the ORs.
There have been some past posts on the subject with additive information, such as the annuities of the Cherokee being held by Southern banks and the publicized view of the Republicans that it wouldn't be long until the Indians had to give up the Indian Territory for white settlement. Both of these issues were used effectively to influence the Cherokee to treat with the South. In May 1861, the US Army withdrew all its troops from the Indian Territory. Of course, the Confederate victories at Wilson's Creek (where some Cherokee participated) and 1st Bull Run were strong influences as well. The provisions of treaties themselves are good indicators of what was important to the "Five Nations in Alliance with the Confederacy".