MARSH WAKBLER 



in certain districts at the commencement of May. Thus it 

 seems as if the period of arrival were not yet adjusted to the 

 environment in which the bird now finds itself, but that a 

 gradual adjustment is taking place. 



Impressed with the possibility of some change having 

 recently been effected, we turn our attention to the points of 

 similarity or difference in the characters of the two species, 

 hoping thereby to find some indication of the nature of the 

 change. Structure and colour tell us but little beyond the 

 intimacy of the bond; they point to the probability of the 

 two forms having originally been the same, but they afford no 

 clue as to which is the more recent development. The 

 emotional behaviour gives greater hope of success, for although 

 the song and motor reactions of the Marsh Warbler are widely 

 differentiated from those of the Eeed Warbler, we nevertheless- 

 find in the former the rudiments of the special features char- 

 acteristic of the latter. We may say of the Marsh Warbler 

 that there is a general heightening of the manifestation at all 

 emotional periods. The song is more vigorous, possesses a 

 wider range of tone, includes a greater number of imitations 

 and is produced with but little hesitation. The visible organic 

 symptoms of the emotions which accompany the instinct of 

 pugnacity and the reproductive and parental instincts are 

 more suffused with feeling tone, more frequent in occurrence, 

 and appear to be more readily provoked. May we not there- 

 fore speak of its nervous system as a higher and probably 

 more recent development ? Now we concluded from our 

 examination of the dates of its arrival in different countries, 

 the variation in its nest-building instinct, and the small 

 dimensions of its breeding territory, that its environment may 

 have been at one time similar to that now inhabited by the 

 Eeed Warbler. Assuming then that we are thus far correct 

 in our speculations we shall find it difficult to conceive of such 

 a development of the nervous system and such a change of 

 environment as a coincidence and nothing more. We are 

 justified in believing that there must be some relation between 



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