The migration of the White Stork (Ciconia ciconia): a special case according to new dataTo formulate a comprehensive plan for the conservation of the White Stork (Ciconia ciconia) in conformity with the "Bonn Convention", along the eastern migration route from the breeding grounds across Israel into the staging areas in northeastern Africa, it was essential to investigate the entire process of migration, including resting behaviour as well as the energetic and ecological aspects. Our approach employed satellite tracking (of 75 individuals), observations of storks in aviaries by methods including magnetic resonance imaging (MRI) and spectroscopy (MRS) (12 birds over 15 months), and extensive field studies. The main result of the investigation is that the White Stork exhibits, at least on the eastern route, a particular mode of migration not previously described in this form for any bird species, with the following characteristics: (i) very rapid travel from the breeding region into the North African staging areas, normally with flight periods every day, lasting about 8-10 hours and separated by 14-16 hours of rest. The ca. 4 600-km distance to latitude 18°N is covered in an average of 18-19 days by both young and adult storks. (ii) Rest periods of a whole day or even several days are the exception, and their occurence seems to be prompted by external circumstances rather than prescribed in the endogenous migration program. (iii) Body mass and fat deposition are low during the outward (and the homeward) journey and peak in midwinter, which is interpreted as an adaptation to unpredictable conditions in the winter quarters. (iv) There is no discernible hyperphagia during migration; instead, on the outward journey the storks evidently feed mainly to meet their immediate needs when in eastern Europe, more opportunistically when approaching the Mediterranean Sea, and practically not at all in Israel. According to this observation and the comparison of body weights in Sachsen-Anhalt and Israel, it is likely that storks lose weight on the outward trip and do not regain it until they reach Africa. We call the migration mode of the White Stork, which travels predominantly in gliding flight, the MSOM type (from "mostly travelling every day", "seldom inserting whole-day rests", "opportunistically feeding" and "moderate or no fat depots developing"), and distinguish it from the types ILHB (for intermittently migrating) and NNHB (migrating non stop) (see Discus-J. Ornithol. 142, 73-92 (2001)  Deutsche Ornithologen-Gesellschaft/Blackwell Wissenschafts-Verlag, Berlin ISSN 0021-8375 U.S. Copyright Clearance Center Code Statement: 0021-8375/2001/14201-073 $ 15.00/0 sion). The results of this study, in particular regarding fat deposition and state of breast musculature, are based substantially on MRI and MRS; these methods, tested here in a pioneering long-term study of a bird species living in the wild, have proved extremely useful and show great promise (see following paper).

Physical condition of migrating Steppe Buzzards Buteo buteo vulpinus was determined during spring migration at Elat, southern Israel, 1984–1988. An index based on measurements of body mass, wing‐length and culmen was used to estimate fat content, based on fat extraction from nine buzzards. In addition, hydration condition was measured in 1988 and moult was checked in 1985–1988. More immatures (1001) than adults (459) were trapped, and a greater percentage of immatures (19.8%) than adults (8.4%) was retrapped during the same season. Adults had significantly greater fat reserves (4.5% of body mass) than immatures (3.8%). Most adults were in some stage of interrupted moult: however, active primary moult was noted only in immatures (10%). These findings suggest that different age groups use different migration strategies. Most of the buzzards trapped in this study could not have completed their entire migration using only stored fat: thus, hunting was probably necessary to replenish their energy reserves. No indication of water stress was found in the spring of 1988.

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