1 8 OUR SUMMER MIGRANTS. 



nett, 1875, pp. 56, 57, will be found a long foot- 

 note on the subject, with woodcuts illustrating 

 the comparative form of the wing in these three 

 birds. Mr. Blake- Knox, in "The Zoologist" 

 for 1866, p. 300, has pointed to the second 

 quill-feather, depicted in a sketch accompany- 

 ing his communication, as being an unfailing 

 mark of distinction.' When we reflect, how- 

 ever, upon the variation which is found to 

 exist in the length of feathers, owing to the age 

 of the bird, moult, or accident, too much stress 

 ought not to be laid upon this as a character. 

 At the same time there is no doubt that, taken 

 in connection with other details, it will often 

 assist the determination of a species. After 

 examining a large series of these birds, I have 

 come to the conclusion that, as regards the 

 wings, the following formulse may be relied on : 

 Wood Warbler, 2nd=4th; 3rd and 4th with 



> Mr. Blake-Knox subsequently corrected his statement, 

 remarking that he had by mistake written second instead oi 

 third primary quill. The first primary is so rudimentary as 

 almost to escape observation. 



