Visual display of the Aldo Leopold papers : 9/25/10-6 : Writings

Aldo  epl 
Sinc 1       I have recorded the weights of some 600 
6noks of fifteen species killed mostly in the upper Rio Grande 
Valley of New Mexico. The seasonal variations in l*eights and 
their apparent relation to 2plumage changes have been described 
in previous papers. 
It occurred to me that duck hunters have a further 
opportunity of contributing to ornithology by determining the 
interrelations of weight and various body measurements. Ac- 
cordingly, ea   body measurements were taken on 23 mallards 
killed during December, 1922, October and Deoember, 1923, and 
January, 1924, at various points in the upper Rio Grande Valley 
of New Mexicb, and on 21 mallards killed in Henderson County, 
Illinois, November 5-7, 1925. All these birds were weightd 
on the same scales, but unfortunately the body measurements, 
with the exoeption of bill and length, are not comparable 
throughout. In the New Mexico birds, spread was taken; in IlUiois 
the standard wing measurement. Length of foot was taken in New 
Mexico, but not in Illinois. This lack of standardization 
prevented complete statistical analysis of the non-standardiz- 
"Notes on the weights & plumage of ducks in New Mexico" Condor

XX, Mayo 1919, pp.128-129. 
"Weights & plumage of ducks in the Rio Grande Valley", Condor
May, 1921, pp. 85-86.* 

The following analysis and conclusions are offered 
in the full realization that a larger number of birds would 
be desirable, although some of the relationships indicated 
by the graphs are so positive that it seems doubtful whether 
more data would change them. The original purpose was to 
demonstrate a new way to make the game bag yield something 
more than meat, and this, at least, has been done. The task 
of analysis also clearly demonstrated the author's mathe- 
matical deficiencies, and while the very best mathematical 
methods have probably not been used, the work has been re- 
viewed by               of the Forest Products Laboratory, who 
says - 
The clearest presentation will result, I think, from 
Llowing the analysisstep by step4and building up the conclu- 
Graphs 1 & 2 
The birds were arranged in ascending order of weight 
New Mexico and Illinois separately, the weights plotted 
points, and the points Joined to form an unsmoothed "fre- 
noy curve" for weight. 
Next, the various body measurements were plotted for 
ea6h bird, arbitrarily adjusting the tertical scales so that 
the total range in each measurement would equal.on the graph,