Species' common names were designated as keywords. Birds were further described by the keywords "primary cavity-nesting bird" or "secondary cavity-nesting bird". Mammals were described by the keyword "mammal", and bats were given the additional keyword "bat".

Geographic areas were given keywords representing the continent and country where the research took place. North American areas were further subdivided by state or province. Areas within Oregon were given one of the following keywords: Coast Range, Cascade Range, Willamette Valley, Siskyou-Klamath, C Oregon, NE Oregon, or SE Oregon. Areas within Washington were given one of the following keywords: Puget Sound-Olympic Peninsula, Cascade Range, NE Washington, SE Washington, or Columbia Basin.

When possible, we characterized habitats in which the studies took place with one or more of the following keywords: conifer forest, hardwood forest, mixed conifer-hardwood forest, boreal forest, grassland, desert, scrub vegetation, agricultural area, and riparian forest. For North American temperate forests, habitats were given keywords representing the common names of the dominant tree species present.

We described the biological content of each paper by using one or more keywords . If we were not able to determine whether a certain biological aspect was actually examined in the paper, we listed the appropriate keyword followed by a question mark.

We included two additional fields in our bibliography, one to note how the citation was located, and the other to note how the paper was described. Notes: This Procite field shows how the citation was located. If it was located during a systematic search, “Search” was entered; if it was suggested by a reviewer or identified by our own personal knowledge, "Not found in search" was entered. Call number: This Procite field shows how the paper was described. If we consulted the actual paper, “From article” was entered; if we used the title, abstract, or keywords from a bibliographic database to describe the paper, “From abstract” was entered.