48 (3) :291 301 , 2002 Acta Zoologica Sinica BIRD MIGRATION : THE PRESENT VIEW OF EVOL UTION, CONTROL , AND FURTHER DEVELOPMENT AS GLOBAL WARMING PROGRESSES Peter BERTHOLD ( Max Planck Research Centre for Ornithology , Vogelwarte Radolf zell , Schloss Moeggingen , D2 78315 Radolf zell , Germany) Abstract Studies during recent decades have shown that bird migration in general is to a great extent under direct genetic control. There is evidence indicating the existence of an innate migratory drive as well as genetic control of (i) the onset , duration and end of the migration period , (ii) the amount of migratory activity , a genetically prescribed parameter that determines the distance over which the bird flies , (iii) the migration directions and (iv) physiological parameters , in particular fat deposition during the migratory period , but also those determining which individuals will migrate and which will not in forms that are obligatorily partial migrants. A two 2 way selection experiment has shown that within only a few generations partial migrants can be converted by selection into pure migrants or nonmigrants. Selection for a new migration direction , leading to new winter quarters , can occur equally rapidly in free 2 living birds. At least in the species most closely studied so far (the blackcap , Sylvia atricapilla) , the attributes migrant or nonmigrant are inherited in conjunction with the characteristic amount of migratory activity (as a time program) , and the former are evidently controlled by a threshold mechanism. A new bird 2migration theory postulates that even in forms that at present are exclusively migratory , selection for lower levels of migratory activity can cause a threshold to be crossed , below which nonmigrants appear. Accordingly , conversion of a population from migratory to nonmigratory can occur by selection with a transition through partial migration. This intermediate stage is prevalent among the recent bird species ; it appeared early in the evolution of organisms and in the case of birds was probably acquired from ancestral , pre 2 avian forms. Model calculations indicate that with strictly directed selection , migratory birds can be converted to sedentary in about 40 years and conversely. This explains the changes in migratory behaviour currently observable in so many bird species in the course of global warming; in particular , migratoriness is decreasing in various respects at higher latitudes. The new theory also enables us to predict the ways in which avifaunas are likely to be restructured if warming continues; these scenarios are briefly outlined. Key words Birds , Migration , Evolution , Genetics , Global warming Received 24 September , 2001 ; revised 25 March , 2002 Brief introduction to the author Dr. Peter Berthold , Professor. Main research interests : avian migration , population dynamics , behavioural and population genetics ( mainly related to avian migration) , experimental evolutionary studies , further annual rhythms , breeding biology , changes of bird life in relation to global warming. E 2mail : berthold @vowa. ornithol. mpg. de 1 Introduction Our institute , the Vogelwarte Radolfzell , was established 100 years ago , in 1901. It was then called Vogelwarte Rossitten and was situated in East Prussia , far to the northeast of its present site. The first ornithological 2 biological observation station in the world , it was brought to life as a result of proposals made at the First International Ornithological Congress , held in 1884 in Vienna. From the outset it was directed primarily towards the study of bird migration , and throughout its history it became progressively more focused on that area of research. It was only for a short period that the work relied on pure field observations. Beginning as early as 1903 , data were obtained from a broadly based ringing system , an approach that had recently been developed in pioneer studies by the Danish teacher C. C. M. Mortensen. By the time that the end of World War 2 brought activities at the original institute to a halt , about a million birds had been ringed. Since the institute was re 2 established at Radolfzell in 1946 , the number has risen by about 415 million. The insights obtained from recoveries of