Conceptual approaches to avian navigation systems

Abstract

The general basis of migratory orientation in birds is most probably an endogenous time-and-direction programme. Directions are selected with respect to celestial as well as geomagnetic clues. These clues appear to be integrated within a system that profits from the special advantages of either kind of environmental signal, and thereby can cope with their limitations. Using these clues, and following a genetically determined intended direction (or sequence of directions) over a genetically determined period of time, a bird may reach a larger population-specific area, but it will hardly be able to find a particular location, such as, for instance, its previous breeding site. Homing to a familiar site over several hundred kilometres of unfamiliar terrain is substantially based on the smelling of atmospheric trace compounds. At shorter distances from home, orientation by means of (presumably visual) familar landmarks completes the repertoire of mechanisms guiding a bird back home. These mechanisms are based on different kinds of "maps' and "compasses'. -from Author