162 Trowbridge — Interlocking of Emarginate 



The primaries of the left wing we re lifted out of the notches 

 and the third primary subjected to measurement. The recov- 

 ery of this feather from the pressure caused by the interlock- 

 ing is shown in Series 16, fig. 11. The notches in the other 

 feathers were as wide as the feather measured and disappeared 

 gradually approximately at the same rate. It is seen that the 

 notch decreased in width from 1-S to 1*8 millimeters in about 

 two hours. In the case of this hawk a little over two minutes 

 were lost before the feather was unlocked and subjected to 

 measurement, but it has already been shown that it requires 



14 































































































































































































































































































































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N 

















































































































































































,0 

























































































































16 











































































































































































































































































































































































































































10 



f-0 50 



Time 



70 BD 

 Minutes. 



9 



Fig. 14. Series 16. Kecovery of the web of the 3d primary of the left 

 wing of a Marsh hawk, Circus hudsonius, shot Sept. 21st, 190o, 9.26 a. m., 

 at New Haven, Conn. lst-4th primaries of left wing found interlocked. 



ten to twenty minutes to form the smallest notch. So that 

 this time (2 minutes) was a small factor in the time of forming 

 the notch. 



V. Species which have Emarginate Primary Feathers. 



The emarginate formation of the primaries is more pro- 

 nounced in the Raptores than in any other birds, especially in 

 the case of the sub-order of Accipitres, or diurnal birds of 

 prey, eagles, hawks, etc. Some of the family of Cathartidae 

 or American vultures have a number of their primaries emar- 



