Trowbridge — Primary Feathers in Flight. 145 



Art. XI. — On the Interlocking of Fmarginate Primary 

 Feathers in Flight; by C. C. Trowbridge. 



This paper contains the results of observations showing that 

 certain birds interlock the emarginate primary feathers of 

 their wings in flight. Some of these observations were made 

 a number of years ago, but were withheld from publication 

 until sufficient evidence could be collected to demonstrate con- 

 clusively the existence of this principle of animal mechanics. 

 The additional evidence has been obtained and the complete 

 paper is now presented. 



A paper published in 1887, entitled "Something New 

 About the Flight of Birds,"* contained a short account of an 

 observation which I made during the autumn of 1885 ; namely, 

 that on several occasions some of the primary or long end 

 feathers of wings of hawks were found interlocked when these 

 birds were killed while in flight. The primaries found inter- 

 locked were those which were emarginate, that is, having their 

 webs narrowed half way to the tips (as shown in fig. 1), the 

 feathers being interlocked in the emarginations. 



The essential facts of the observation were also presented by 

 my father, the late Professor W. P. Trowbridge,, before the 

 National Academy of Sciences and the New' York Academy 

 of Sciences, and shortly -afterwards a controversy on the sub- 

 ject took place in Science between the late Dr. Elliot Coues, 

 who opposed the hypothesis that the primaries were inter- 

 locked in flight,! an< ! the late Professor J. S. Newberry and 

 Professor Trowbridge, who took a strong stand in its favoi'4 

 Investigation of} the subject has been continued by me with 

 the purpose of obtaining further facts. 



In September, 1891, at New Haven, Conn., during the 

 migrations,! a large number of hawks were killed and exam- 

 ined as soon as they fell to the ground. The observations on 

 ■one occasion were assisted by my father and on another by Mr. 

 Henry Townsend of .New Haven. These and later observa- 

 tions have been presented before the New York Academy of 

 Sciences but have not been published heretofore. 



The alleged interlocking or overlapping of the primaries 

 has been repeatedly disputed by prominent ornithologists, a 

 fact which has caused me to defer the publication of a paper 

 on the subject until I could decide the question positively. 



*0. C. Trowbridge, 0. & O., vol. xii, No. 12, p. 202. 

 fSci., vol. x, No. 250, p. 321. % Ibid., vol. xi, No. 257, p. 9. 



§ C. C. Trowbridge, Hawk Flights in Connecticut. The Auk, xii, No. 3, 

 July 1895. • 



