An often-overlooked source of insight into the rules and process of consultation are the preambles to regulations. Any time a regulation is put in place, or changed, it has to be published in the Federal Register (the “Government’s Newspaper”) https://www.federalregister.gov/. I have posted what I think are the 3 most relevant Federal Register notices for consultation practitioners on our Resources page. These include the 1986 Regs Consultation Final (FR-1986-06-03), the 2015 Incidental Take Final (FR-2015-05-11), and the 2016 Destruction and Mod Final (FR-2016-02-11). Some of the regulations described in the linked documents have changed, but much of the discussion on concepts is still relevant.
As a part of the published document (often a major part) the agency promulgating the regulation explains in detail their choice of wording, answers public comments, and often explains the thinking behind the concepts embodied in the much briefer regulatory text. This preamble appears first in the federal register notice before the actual regulatory text. Though it is dry, and the federal register is often formatted in an archaic 3 column style – the preambles contain very good context for the regulations that follow in the document. When I first started in consultation, we had to read hard copies word-by-word to find the items of interest. Today using word search features, the preambles are much easier to use and should be a go-to for practitioners for more insight into consultation and terms that are used.