CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF 
THE MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD 
COLLEGE. E. L. MARK, DIRECTOR. No. 121. 
A QUANTITATIVE STUDY OF VARIATION IN 
THE SMALLER NORTH-AMERICAN 
SHRIKES. 
R. M. STRONG. 
CONTENTS. Pace. 
I. Introduction 271 
II. Material S 273 
III. Methods 274 
4. General Precautions ..... 274 
B. Measurements of Variable Characters 275 
1. Linear Measurements EE A E E OE a ete ow? 275 
2. Curvature of s 45275 
3. Color "eben Ru LUI a ec UIN ere RE E 278 
C. Paci dec 2.1.1 en aig CM rM pue ee Cal eee paid cq LM c E 280 
IV Rete c iced d e e N RAE . 281 
A. indices of Meise POM US MUR Mq UM E . 281 
i. Wing and Tail... eset tentem 281 
2. oe aie and Dp of Bill .. eae S 
à Color e inane PRI areari rani eremi indt Ue peret 286 
B. bum of Constants of Frequency Polygons ..........——— ce 287 
C. a of Results and Conclusions Se Ot EE Hee cum 295 
Ve DHHIMEE Lii eqni e Eea steerer pe tob 297 
Bibliography ui qu Qu DH eL i aeta iem .. 298 
I. INTRODUCTION. 
Tue work described in this paper was begun in the fall of 
1898, and was carried on at Harvard University during the 
year 1898-99 under the direction of Dr. Charles B. Davenport. 
It was completed during the winter of 1899-1900. 
It was my desire to employ statistical methods in the study 
of variation in a group of birds, and to apply the “ Precise 
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