THESES FROM LITERATURE. 



4. not forced by climatical influences, nor by want of food, nor 

 by want of Birds serving as foster-parents (to hatch the eggs), 

 as all these necessities of existence are to be found everywhere 

 on the whole area of its tropical and subtropical distribution. 



5. The reasons for the wandering habits of this Cuckoo are there- 

 fore only explicable by instinct, a relic of an inherited habit. 



6. The facts inferred from the observations on this species are 

 worth remembering by all „as reflecting on the mysteries of 

 Bird-Migration."* 



a) Inductive Theses. 

 Barrington, R. M.:„The Migration of Birds etc." London and Dublin 

 1901. 



For Ireland. 

 1. Some species of migrating Birds are observed only in certain 

 localities along the Irish coasts, which shows the existence of 

 distinct migrating directions. 



2. The majority of Birds of Migration arrive at a period of con- 

 siderable evenness, which leads to the conclusion that, at their 

 departure from Ireland, they arrive at the same time. 



3. The departure is dependent upon the force, not upon the direc- 

 tion of wind. 



4. The Migration direction is generally landward. 



5. The first arrivals in spring are long-winged species; in autumn 

 out of 14 cases there were 9. in autumn the long-winged males 

 of Turdus merula depart first ; the females last (errors with 

 young Birds not excluded). Whether the young Birds depart 

 before the old ones could not be ascertained. 



6. Less powerful fliers migrate mostly by night, probably for 

 safety's sake. 



* Original contribution by Dr. O. Finsch. 



tea 51 10 



