Recently published Ornithological Works. 149 



polar extremities took place^ at the close of the Tertiary 

 Epoch, " bird-life must have been crowded thence towards 

 the tropics, and the struggle for life greatly intensified." 

 The less yielding forms became extinct, those less sensitive 

 sought to extend their range by a removal northwards in 

 summer, only to be forced back by the recurrence of winter. 

 This incipient change of locality, according to the seasons, 

 extended itself and became habitual, " and through the 

 heredity of habit gave rise to that wonderful faculty which 

 we term the instinct of migration /■* To this theory 

 Mr. Chapman wishes to add a few words concerning ''the 

 influences which may have aided climatic conditions in 

 establishing the habit of migration." These influences are, if 

 we rightly understand Mr. Chapman, ''the instinctive desire 

 for seclusion during the period of reproduction," which drives 

 birds northwards in spring, and the " failure of the food- 

 supply," which leads them to desert their breeding-grounds 

 on the approach of winter and to return south again. 



In his second paper Mr. Chapman gives a popular account 

 of the facts recently ascertained in America as to the migra- 

 tion of birds by night, which undoubtedly takes place, 

 whether the phenomenon be habitual or abnormal. On 

 Sept. 26th, 1891, it was his "good fortune" to pass the 

 night in company with other ornithologists at the Bartholdi 

 Statue at the moutb of the Hudson-River valley, in order to 

 witness the migration. The first bird entered the area illumi- 

 nated by the torch on the Statue at 8 p.m. During the next 

 two hours birds were constantly heard and many Avere seen. 

 About 10 o'clock, when a light rain began, there were 

 hundreds of arrivals, and the " air was filled with the calls 

 and chirps of the passing host." The ornithologists then 

 ascended to the torch, and remained for two hours, during 

 which thousands of birds passed within sight. At daybreak 

 a few stragglers were still to be seen winging their way 

 southward. 



Mr. Chapman describes the following ingenious mode of 

 observing the nocturnal migrants by a telescope. A com- 

 paratively low-power glass is focussed on the full moon 



