THE PERILS OF MIGRATION. 169 



people have remarked the great gatherings of 

 Swallows, Martins, and Swifts, just previous to 

 migration in autumn, yet where do we see such 

 similar multitudes in spring? The majority of 

 these birds are young ones, neither so strong of 

 wing nor so robust of frame as their parents, and 

 it is among these that the highest mortality is 

 reached. The death-rate of a large town standing 

 at say fifty or sixty per 1000, creates something 

 like a panic among its human inhabitants ; but 

 there can be no doubt whatever that the death-rate 

 among birds on migration reaches ten times that 

 amount per 1000, and during excepdonal circum- 

 stances very much more ! From the moment that 

 a migrant bird sets out on its journey it is exposed 

 to quite a new set of dangers, whilst many other 

 ordinary perils of its existence are very much in- 

 tensified. From one end of its fly-line to the other 

 successive dangers surround it, and enemies of 

 every kind have to be eluded. Migration then, 

 instead of being a pleasant path in the wake of 

 retreating summer or in the van of advancing 

 spring, is the most fatal undertaking in the life of 

 migrant birds, and few there be that survive it. 



The Perils of Migration may be divided into three 

 important classes, viz. those arising from Fatigue, 

 due to the mechanical portion of migration flight ; 

 those arising from the Natural Enemies of each 

 species; and those arising from Blunders and 

 Fatalities on the way. Probably the first class of 

 perils is the most fatal one ; a journey with little 



