° ' 192 o \ Recent Literature. 47c/ 



dition on the coloration of the Ground Dove? That single experiment 

 is quoted more than perhaps any other in exploiting the evanescent char- 

 acter of subspecific differences and so far as we know it has never been 

 checked nor has very serious consideration been given to food or a variety 

 of other factors that may have entered into it. — W. S. 



Rowan and Others on the Nest and Eggs of the Common Tern. 1 

 The egg collector who applies for a collecting permit on the ground that 

 he is engaged in "scientific research" would do well to consult this paper 

 in order to appreciate the opportunity for real scientific research that is 

 offered in the study of birds eggs. Only expert mathematicians will be able 

 to follow intelligently the computations and calculations which are pre- 

 sented but the results and hypotheses are of interest to all. Briefly stated 

 the work here reported consisted in the measurement of some 800 clutches 

 of Tern's eggs with notes on the character of the markings and shade of 

 color of the eggs and the nature and location of the nests in which they 

 were deposited. With these data it was possible to prepare tables and to 

 determine the probable correlation between certain measurements and 

 colors, or between measurements and colors and character of nests, as 

 well as the cause or meaning of differently colored eggs in the same nest. 

 The work was accomplished by three field workers, one reporter and three 

 tabulators and computers, and was in reality a continuation of a similar 

 study carried on in the previous year. The final results show that the 

 eggs averaged larger in 1914 than in 1913 and exhibited more uniformity, 

 both due apparently to the bad season of 1913, when the very young and 

 very old birds may have perished, and to the exceptionally favorable 

 year of 1914, when food was unusually abundant. 



In regard to shape of egg and character of nest it was found that the 

 more nearly spherical eggs were in the most careless, and loosely con- 

 structed nests, while the denser brown and lighter green eggs were more 

 often in nests without much material, i. e., mere hollows in the ground. 



The resemblance of the color pattern to the nest brings in all sorts of 

 complications. With eggs as variable as those of the terns it is incon- 

 ceivable that the bird has, when building her nest, any conception of what 

 her eggs are going to be like. As the authors say such an instinct would 

 be conceivable in the case of a species laying uniform eggs and building 

 a specific type of nest, but not in the present case. The fact that the 

 terns were frequently found to begin laying before they gathered any nest 

 materials would raise the possibility of their adapting the materials to the 

 character of the eggs. Then comes the possibility of there being two 



1 On the Nest and Eggs of the Common Tern (S. fluviatilis). A Comparative 

 Study. W. Rowan, E. Wolf, and the late P. L. Sulman, Field Workers; Karl 

 Pearson, Reporter; E. Isaacs, E. M. Elderton, and M. Tildesley, Tabulators and 

 Computers. Biometrika, Vol. XII, Nos. 3 and 4, November 26, 1919, pp. 308- 

 354, plates II-VI. 



