62 GOLDEN WARBLERS. 



While not attempting to prove a separate remote ancestral origin for the 

 Golden Warblers apart from the Wood Warblers, I do believe, all things con- 

 sidered, that they have formed a distinct group which has now no immediate 

 connecting link to bind it to any other similar group (see, however, remarks un- 

 der head of Allied Species ). 



Habits. As these are the strongest factors in establishing natural groups 

 among all animals, through evolving changes in organisms, vvg will next consider 

 them. All of the Wood Warblers are quite arboreal in habit inasmuch as they 

 inhabit woodlands, or at least thickets, ihe Prairie and its allied form of the Cay- 

 man Islands, being partial exceptions to the rule, but the Golden Warblers are 

 as far as I have seen, inhabitants of the open country. 



Now let us see what changes have been brought about in these birds through 

 their habits of livin'g in different kinds of country. In the woodlands, which, as 

 seen, are the homes of the Wood Warblers, insects, upon Avhich all warblers 

 mainly feed, are abundant, but they are largely the larvae, many being the soft 

 catsrpiUars of lepidopterous insects. Warblers are particularly fond of these, 

 but this class of insects in the earlier stage of their cxistance, are, through protec- 

 tive coloration and habits of concealment, not very easy to find, even by a keen- 

 eved warbler. On the other hand, insects which are eaten by warblers are not 

 as abundant on low shrubbery in open fields as they are in woodlands, but those 

 which do occur there are more easily seen, yet might be more difficult to capture. 

 With different game to hunt under different environment, this game vary- 

 ino- inhabit, the warbler of the woodlands must employ somewhat different meth- 

 ods in capturing its prey from those practised by the Avarbler of the open country. 

 The woodland hunting warbler would have to be intelligent enough to un- 

 derstand the color mimicry of one group of caterpillars, and good eyesight enough 

 to detect the hiding places of other groups. 



That the Wood Warblers are comparatively intelligent is shown by the large 

 size of the cerebrum, and that they possess superior powers of sight by the large 

 optic lobes, as typified by the Chestnut-sided Warliler. 



In contrast, the Yellow Warbler has a smaller cerebrum and optic lobes, for 

 it does not require as much intelligence, nor as good eyesight to capture its prey 

 in the more open country. 



One species of warbler would have to be about as agile as the other, hence we 

 do not find any great difference in the size of the cerebellums, or lesser brains. It 

 would be an advantage, however, for a warbler in capturing its prey in an open 

 country to be able to reach a little further for it, thus we find the neck of the 

 Yellow Warbler a little longer than those of the Wood Warblers. As the food 

 of the Yellow Warbler does not consist of as quite such soft material as that of 

 the Chestnut-sided, its digestive system is larger and stronger, necessitating a 

 larger body cavity. With this enlarged alimentary canal and longer body, we 



