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hurlbertlab / dietdatabase

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Unspecified fraction diet #58

Closed ahhurlbert closed 3 years ago

ahhurlbert commented 7 years ago

The diet data from Beal compendia are never explicit about what fraction of diet is being reported (% Items or % Wt_or_Vol).

The introduction to Wheelwright 1986 discusses U.S. Biological Survey Records and Beal data, and implies that these records are all % by volume.

Thus we should change "Unspecified" to "Wt_or_Vol" for all Beal studies.

ahhurlbert commented 7 years ago

To clarify, some of the data Beal reports are clearly % Occurrence, and these should not be changed.

But Unspecified should be changed, and records where Diet_Type is "Items" should be re-examined as that may have been a guess that also be changed to "Wt_or_Vol".

ahhurlbert commented 7 years ago

Maybe since @thenness is checking Beal papers for duplicates he can keep an eye out for any language that might confirm that some of the diet data is % by Items. If no such language is found, then I think we convert at "Items" in Beal studies to "Wt_or_Vol".

thenness commented 7 years ago

Agreed. Other than when the papers are clear about occurrence data, there's no indication that any different method is being used so I've been changing the Items and Unspecified entries to Wt_or_Vol as I go. I believe I have almost all the Beal entries edited this way, will double check.

ahhurlbert commented 5 years ago

Judd 1901 "The relation of sparrows to agriculture" writes in regard to the methods employed by the Biological Survey:

"After each element in a bird's stomach has been identified and placed in a separate pile, the percentages of the different elements are estimated by volume." (p. 14)

ahhurlbert commented 5 years ago

Re-evaluate all studies in the db that list Diet_Type as Unspecified. If they are from the early 20th c and/or related to efforts by the Biological Survey, then change to Wt_or_Vol.