152 



Trowbridge — Interlocking of JE/marginate 



IV. Measurement of Notchhs in the Primary Webs show- 

 ing HOW LONG THESE FEATHERS WERE INTERLOCKED. 



It has been suggested that the interlocking of the feathers 

 in the many instances which have been recorded was accidental 

 and took place while the birds were falling to the ground. 

 Perhaps a few primaries were thus accidentally interlocked 

 after the birds were shot ; on the other hand, it is probable 

 that as many or more of the emarginate primaries if inter- 

 locked while the birds were flying became unlocked when the 

 birds were struck by shot and fell. This matter has been 

 carefully investigated and the fact demonstrated that the 

 feathers interlocked were in that condition either intermit- 

 tently or continually for several hours previous to the death 



of the birds. Considerable difficulty has been experienced in 

 obtaining the necessary observations. During the past few 

 years not less than thirty trips have been made to a hill five 

 miles from New Haven, Conn., in the autumn, and ten trips to 

 the Watchung Mountain range near Paterson, JNL J., in the 

 spring. Many times large numbers of hawks were observed 

 but none could be obtained, owing to the fact that they were 

 migrating with a fair wind at an altitude that was beyond gun 

 range. The observations were finally collected and are given 

 herewith. 



When hawks are shot while they are flying, deep notches 

 are found in the edges of the posterior webs of the emarginate 

 feathers that are interlocked. In unlocking the feathers it is 

 necessary to lift them free of these notches. (See N, fig. 6.) 

 The notches are due to the pressure of the feathers which 

 have been in contact. It occurred to me that the immediate 

 disappearance of the notches on unlocking the primaries would 



