° 1918 J Clark, Tail-feathers and Coverts. 115 



Woodpecker, covert 1 lies between the bases of rectrices 2 and 3. 

 On the other hand in young birds and sometimes in adults, covert 1 

 is directly over rectrix 1 and each succeeding covert overlies its 

 own rectrix. 



The relative size of the different major coverts is also a matter 

 which shows some diversity, though as a rule covert 1 is largest and 

 the size decreases quite uniformly to the outermost member of the 

 series, which is the smallest. Not infrequently however, at least 

 among water-birds, covert 1 is distinctly smaller than 2, and occa- 

 sionally, as in the bittern, it is very small. Sometimes the third 

 or fourth covert may be the largest, the second and first about 

 equalling the fifth and sixth. The most extreme case is that of the 

 cormorants, where the three outer coverts are large and well- 

 developed with 6 the largest, 5 smaller and 4 still smaller, while the 

 three inner coverts are much reduced and 1 is the smallest of all. 



According to the relative number of coverts and rectrices, birds 

 divide naturally into three groups: (1) coverts and rectrices of the 

 same number; (2) coverts more numerous than rectrices; (3) 

 coverts less numerous than rectrices. 



In all normal individuals, the tail-feathers of a bird are arranged 

 in pairs, an equal number on each side of the mid-line of the pygi- 

 dium. In the following tables therefore the condition on only 

 one side is referred to. The rectrices are numbered from the middle 

 outwards, no. 1 being next to the mid-line. The major coverts 

 are numbered correspondingly. The formula "6-6" indicates 

 that there are six rectrices and six major coverts on each side of 

 the pygidium; "6-4" shows six rectrices but only four coverts 

 while "8-6" shows eight rectrices and six coverts. The number 

 of rectrices is invariably placed first. 



It should be clearly understood, and I cannot emphasize the point 

 too strongly, that the statements made here in regard to number 

 and position or size of the coverts and rectrices are based wholly 

 upon my own recent and hasty observations. They are thus liable 

 to correction, particularly with reference to the larger groups. 

 When I say for example that the Passeres have six rectrices and 

 only five coverts, I am not ignorant of the fact that some Passeres 

 have seven rectrices. I merely know nothing about the number 

 and position of the major coverts in such cases, so, for the purpose 



