SEXUAL CHARACTERS IN BIRDS. 



Table IX. 



671 



Notes. — Compiled from F. Finn's ' The World's Birds.' 

 Of the remaining birds no note is made e.xcept Passerine birds, which are described 



as sometimes sociable. 

 Some birds form coveys or family associations out of the breeding-season — giMne- 



birds, for instance, and other birds form flocks, e. g. ducks. 

 Reference Nos. :— 1 Soc. 1, 2, 4, 9, 18, 22, 25, 30, 35, 36, 43, 48 : 2 Soc. 7. 33, 42, 



44: 3 Soc. 47 : 1 Non-soc. 8, 28, 32, 45 : 2 Non-soc. 3, 10, 12, 20, 26, 27, 



31, 39, 50 : 3 Non-soc. 21 : 4 Non-soc. 5, 16, 19, 24, 49. 

 Secondary sex characters classified as before. 



Birds may also avoid enemies b}' Laving a habitat wbei/e tliey 

 are free from enemies — for instance, mountain-tops, islands, 

 arctic regions, oceans. Oceanic species are included in Table J. 

 The only other material with which it has been found possible to 

 examine this question is Seebohm's monograph of the Turdida? ; 

 for in this family there is a suilicient number of insular and 

 continental forms for comparative pui'poses. Table X. sets oat 

 the material, and it can be seen that secondary sexual dimorphism 

 is much less common in insular than in contiiiental species. Of 

 the four continental species of the genus Merihla which present 

 little secondary 'sexual dimorphism, it is noteworthy that there 

 are three living high up on volcanic mountains. 



Table X. 



Note. — Compiled from H. Seebohm's ' Turdidte.' 



Endeavours were made to find other material in order to sub- 

 stantiate or not this remarkable coiTelation, but none was found 

 sintable for classification. 



46* 



