156 STUDIES IN BIRD-MIGRATION 



now undertaking their first migratory journeys, and are 

 prone to stray from the accustomed routes to winter 

 quarters followed by their kind. These erring youngsters 

 form the great majority of the waifs visiting us at this 

 season. Casuals of no less than 120 species have from 

 time to time occurred in the British Islands. 



During the great autumn movements, the emigratory 

 ones in particular, migrants are frequently observed 

 simultaneously on all our shores ; and under certain 

 peculiar weather conditions, to be explained in the 

 chapter devoted to migration-meteorology, there are 

 immigratory and emigratory movements simultaneously 

 in progress. 



The autumn migrants (including the birds of 

 passage) as a rule arrive on and leave our shores 

 during the hours of darkness (excepting those which 

 come direct from the east) ; but some emigrant 

 Swallows, Wagtails, Starlings, etc., cross the Channel 

 during the morning, commencing soon after daybreak, 

 and ceasing to do so about mid-day. 



It is chiefly during the great movements of the late 

 autumn that we hear migratory birds passing overhead 

 on dark nights, when proceeding to their inland 

 winter quarters. The object of their calls is probably 

 to enable them to keep in touch with each other. On 

 these occasions they are evidently much alarmed or 

 excited by the lights of our cities and towns, and hence 

 a babel of tongues which disturbs the quietness of the 

 night, recalling to mind Longfellow's beautiful lines — 



I hear the cry 



Of their voices high, 



Falling dreamily through the sky, 



But their forms I cannot see. 



