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The effect of body mass and fat reserves on the choice of the stopover place and on the stopover period was investigated in 3 species of passerine birds migrating through the Sahara in Egypt. Birds grounded in an oasis with food and water were more than 10% lighter than those from a desert stopover place which offered shade only. Stopover period was in(More)
Samples of flight and leg muscle tissue were taken from migratory garden warblers at three different stages of migration: (1) pre-flight: when birds face an extended flight phase within the next few days, (2) post-flight: when they have just completed an extended flight phase, and (3) recovery: when they are at the end of a stop-over period following an(More)
Garden warblers are able to learn an association between time of day and feeding place. In constant dim light and constant food availability, the learned feeding pattern (successive visits to four feeding rooms for approximately 3 hr each) persisted for at least 1 day in three birds and for at least 6 days in one bird. The free-running feeding rhythm had a(More)
In birds, gonadal size varies between fully functional and maximally sized during reproduction and a regressed state with limited function during the non-reproductive periods. Recent findings show that testicular mass of the long-distance migratory garden warbler begins to increase during spring migration. Therefore, we sampled garden warblers during spring(More)
The energetic demands of long-distance migratory birds change drastically, depending on the stage of their life cycle. Changing demands are reflected in the up and down regulation of adipose tissue and organ mass. This paper presents new data on organ size changes during different stages of spring migration of garden warblers (Sylvia borin). Phenotypic mass(More)
Many bird species steeply increase their body mass prior to migration. These fuel stores are necessary for long flights and to overcome ecological barriers. The elevated body mass is generally thought to cause higher flight costs. The relationship between mass and costs has been investigated mostly by interspecific comparison and by aerodynamic modelling.(More)
Water imbalance during flight is considered to be a potentially limiting factor for flight ranges in migrating birds, but empirical data are scarce. We studied flights under controlled ambient conditions with rose-colored starlings in a wind tunnel. In one experiment, we measured water fluxes with stable isotopes at a range of flight speeds (9-14 m s(-1))(More)
Mass changes of skeletal muscles occur in a variety of species during the migratory period. Phenotypic flexibility of flight muscle mass is considered to represent adaptations of the flight muscle to changing power requirements associated with changes in body mass. We analyzed the relationship between muscle masses and body mass for garden warblers (Sylvia(More)
The metabolic costs of flight at a natural range of speeds were investigated in Rose Coloured Starlings (Sturnus roseus, Linnaeus) using doubly labelled water. Eight birds flew repeatedly and unrestrained for bouts of 6 h at speeds from 9 to 14 m s(-1) in a low-turbulence wind tunnel, corresponding to travel distances between 200 and 300 km, respectively.(More)
Behavioural activity, and core and surface temperatures of 4 unrestrained Galapagos fur seals were recorded in the natural habitat during their first weeks of life. Climatic variables were registered simultaneously. Pup behaviours were divided into bouts of resting (55% of total time), sucking (23%) and other activities (22%). Pups maintained a constant(More)