mobbing

A staccato mobbing call, on the other hand, is given for nest predators and serves as a call to arms, inciting all the nesting birds in the vicinity to harass the potential predator and drive it away. Both calls are sign stimuli. Birds are born knowing little about which species are safe and which are dangerous; they learn this by observing the objects of the calls they hear. So totally automatic is the formation of this list of enemies that caged birds can even be tricked into mobbing milk bottles if they hear a mobbing call while being shown a bottle. This variation on imprinting appears to be the mechanism by which many mammals (primates included) gain and pass on critical cultural information about both food and danger. The fairly recent realization of the power of programmed learning in animal behavior has reduced the apparent role that simple copying and trial-and-error learning play in modifying behavior. Evolution, working on the four general mechanisms described by ethology, has generated a nearly endless list of behavioral wonders by which animals seem almost perfectly adapted to their world. Prime examples are the honey bee's systems of navigation, communication, and social organization. Bees rely primarily on the sun as a reference point for navigation, keeping track of their flight direction with respect to the sun and factoring out the effects of the winds that may be blowing them off course.

The sun is a difficult landmark for navigation because of its apparent motion from east to west, but bees are born knowing how to compensate for that. When a cloud obscures the sun, bees use the patterns of ultraviolet polarized light in the sky to determine the sun's location. When an overcast obscures both sun and sky, bees automatically switch to a third navigational system based on their mental map of the landmarks in their home range. Study of the honey bee's navigational system has revealed much about the mechanisms used by higher animals. Homing pigeons, for instance, are now known to use the sun as their compass; they compensate for its apparent movement, see both ultraviolet and polarized light, and employ a backup compass for cloudy days. The secondary compass for pigeons is magnetic. Pigeons surpass bees in having a map sense as well as a compass as part of their navigational system.