=. 
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84 THE CONDOR Vol xia 
be made much more so by a systematic and painstaking collection and study 
of bird enteroparasites. 
One explanation of the differing lengths of incubation among birds is that 
the incubation length is correlated with the bird’s size, which means in the 
last analysis, its weight. One writer (Bergtold, Incubation Periods of Birds, 
1917) who studied this question was able to find recorded in the ornithological 
literature at his command, the weights of only (approximately) ninety-three 
species, which, together with sixty-seven others secured by his own personal 
efforts, made a total which is less than one and one-half percent of all the 
known avian species. Is it not ridiculous, not to say inexcusably wasteful, in 
the face of this dearth of data, that any one should neglect to weigh a bird 
Fig. 31. FIELD SCALES, FOR WEIGHING BIRDS, 
HERE SHOWN PACKED IN SPECIAI. BOX FOR 
CARRYING, | 
when it comes to the skinning table? It takes but a littie time to weigh an ordi- 
nary bird; a well equipped collector or preparator should have at his command 
a set of small scales, both in his work shop and in his field kit. A compact and 
light set of scales for the field can be made very easily out of a set of moderate 
sized druggist’s beam balances; the writer has made such a set and carries it 
with him on all of his collecting trips, and on excursions when no birds are to 
be collected, but when eggs may be found, and weighed. 
This set of scales was made by the writer, and designed to combine mini- 
mum weight and size, and maximum efficiency. With it the writer has weighed 
birds as large as a crow. When closed it is a compact box, ten inches high, 
seven inches broad, and two and one-half inches thick, its total weight is two 
