Summary
Trans-Saharan insectivorous passerine night migrants stopping-over at a small oasis in Sinai were weighed as frequently as possible, throughout the entire length of fall and spring migration passages. Due to the small size of the oasis and the intensive trapping effort, most stopping-over birds were captured and weighed throughout a sizeable portion of their stopover period. Weights at first capture were either similar in both seasons, or greater in fall than in spring. In some species fall migrants that stayed one day were heavier than those staying longer. In other species, and for all species in spring, weights of birds that stayed one day did not differ from those staying longer. In most species the weight of birds that stayed for more than one day did not vary significantly between arrival and departure, and cases of weight gains were commoner in fall than in spring. Trends of weight changes of an individual during stopover were usually inconsistent, but the longer it stayed, more it gained (in fall), or less it lost (in spring). It is proposed that stopping-over birds do not always resume their migration only after their fat reserves have been replenished, but that their decision to take off, or the reappearance of the migration impulse, are also controlled by a time program incorporated into their endogenous migration scheme, which constantly updates the time left for sampling and refuelling. It seems that in spring less time is allotted for the whole migration program, hence the time constraint overrides then all other tactical considerations, such as the state of fat reserves, and the weather.
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References
Abramsky Z, Safriel U (1980) Seasonal patterns in a Mediterranean bird community composed of transient, wintering and resident passerines. Ornis Scan. 11:201–216
Ash JS (1969) Spring weights of Trans-Sahara migrants in Morocco. Ibis 111:1–10
Bairlein F (1985) Body weights and fat deposition of Palaearctic passerine migrants in the central Sahara. Oecologia 66:141–146
Bairlein F, Beck P, Feiler W, Querner U (1983) Autumn weights of some Palaearctic passerine migrants in the Sahara. Ibis 125:404–407
Baker RR (1978) The evolutionary ecology of animal migration. Helmes & Meier publishers, New York
Berthold P (1984) The endogenous control of bird migration: a survey of experimental evidence. Bird Study 31:19–27
Bibby CJ, Green RE (1980) Foraging behaviour of migrant pied flycatchers, Ficedula hypoleuca, on temporary territories. J. Anim. Ecol. 49:507–521
Bibby CJ, Green RE (1983) Food and fattening of migrating warblers in some French marshlands. Ringing & Migration 4:175–184
Biebach H (1985) Sahara stopover in migratory flycatchers: fat and food affect the time program. Experientia 41:695–697
Biebach H, Friedrich W, Heine G (1986) Interaction of bodymass, fat, foraging and stopover period in trans-Shahara migrating passerine birds. Oecologia 69:370–379
Cherry JD (1982) Fat deposition and length of stopover of migrant white-crowned sparrows. Auk 99:725–732
Connell CE, Odum EP, Kale H (1960) Fat free weight of birds. Auk 77:1–9
Cox GW (1968) The role of competition in the evolution of migration. Evolution 22:180–192
Finlayson JC (1981) Seasonal distribution, weights and fat of passerine migrants at Gibraltar. Ibis 123:88–95
Gwinner E (1977) Circannual rhythms in bird migration. Ann. Rev. Ecol. Syst. 8:381–405
Gwinner E (1986) Internal rhythms in bird migration. Scientific American 254:84–92
Gwinner E, Biebach H, von Kries I (1985) Food availability affects migratory restlessness in caged garden warblers (Sylvia borin). Naturwissenschaften 72:51
Izhaki I, Safriel UN (1985) Why do fleshy-fruit plants of the Mediterranean scrub intercept fall- but not spring-passage of seed-dispersing migratory birds? Oecologia 67:40–43
Kesler Y (1977) Climatic characteristics of southern Sinai. Israel Meteorological Survey, Beit Dagan (Hebrew)
Langslow FR (1976) Weights of blackcap on migration. Ringing & Migration 1:78–91
Moreau RE (1961) Problems of Mediterranean Sahara migration. Ibis 103:373–421, 580–624
Moreau RE (1969) Comparative weights of some trans-Saharan migrants at intermediate points. Ibis 111:621–624
Moreau RE (1972) The Palaearctic-African bird migration systems. Academic Press, London, UK
Moreau RE, Dolp RM (1970) Fat, water, weights, and wing-lengths of autumn migrants in transit on the northwest coast of Egypt. Ibis 112:209–228
Nie NH, Hull CH, Jenkins JG, Steinbrenner K, Bent DH (1975) Statistical Package for the Social Sciences (2nd edition), McGraw-Hill, New York
Pearson DJ (1971) Weights of some Palaearctic migrants in Uganda. Ibis 113:173–184
Pielou EC (1966) The measurement of diversity in different types of biological collections. J Theor Biol 13:131–144
Rappole JH, Warner DW (1976) Relationships between behavior, physiology and weather in avian transients at a migration stopover site. Oecologia 26:193–212
Salomonsen F (1955) The evolutionary significance of bird migration. Biologiske Meddelser 122:1–62
Svensson L (1970) Identification guide to European passerines. Naturhistorika Riksmuseet, Stockholm
Zuckerbrot YD, Safriel UN, Paz U (1980) Autumn migration of quail Coturnix coturnix at the north coast of the Sinai peninsula. Ibis 122:1–14
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Safriel, U.N., Lavee, D. Weight changes of cross-desert migrants at an oasis —do energetic considerations alone determine the length of stopover?. Oecologia 76, 611–619 (1988). https://doi.org/10.1007/BF00397878
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DOI: https://doi.org/10.1007/BF00397878