Locomotion patterns of foraging Coal tits Parus ater in a coniferous forest

The use of alternative searching movements may involve different energetic costs. Therefore, birds may gain some advantage by using foraging techniques that permit a reduction in total energy expenditure. In a mountain coniferous forest the movement patterns of Coal Tits were studied by monitoring birds' foraging behaviour with the objective of detecting possible selection patterns in the relative use of different searching movements that differ in their energy costs. In particular, it was expected that different searching movements would not be used at random and would instead correspond to an energy-saving strategy. When foraging in tree canopies, birds moved more often on a horizontal axis than on a vertical one. The relative use of different locomotion modes depended on the direction taken by the bird. Individuals hopped mainly to move upwards, whereas flight - more costly in terms of energy than hopping - was used more frequently in downward than in upward movement. The reduction of energy consumption through selective choice of searching movements may allow birds to reduce their total energy requirements or to allocate more energy to other daily activities, thereby improving their individual fitness.