GENERAL OBSERVATIONS. 327 



Gibraltar and Tangier, thus refers to the subject 

 in his recently-published volume on the " Orni- 

 thology of the Straits of Gibraltar : " 



" Most of the land birds pass by day, usually 

 crossing the Straits in the morning. The 

 waders are, as a rule, not seen on passage ; so 

 it may be concluded they pass by night, al- 

 though I have occasionally observed Peewits, 

 Golden Plover, Terns and Gulls, passing by 

 day. 



" The autumnal or return migration is less 

 conspicuous than the vernal ; and whether the 

 passage is performed by night, or whether the 

 birds return by some other route, or whether 

 they pass straight on, not lingering by the way 

 as in spring, is an open question ; but during 

 the autumn months passed by me at Gibraltar, 

 I failed to notice the passage as in spring, 

 though more than once during the month of 

 August, which I spent at Gibraltar, myself and 

 others distinctly heard Bee-eaters passing south 

 at night, and so conclude other birds may do 

 the same. 



