In the case of migratory birds, we have again a navigation problem. This time
the flight is done at thousands of kilometers distance. It is clear that the
migratory birds should have a map added to the navigation instruments. The
birds should have in memory a successful story-type model (map) of the wanted
route. The bird will compare the wanted position (given by the story-type
model) with the real position. The real position could be found e.g. by
following the magnetic field of the Earth, by observing the position of cosmic
bodies (Sun, Moon, and stars). It is clear that any supplementary information
is welcome and added to the story-type model, to sustain a successful
operation. The navigation story-type model has been built based on a previous
successful flight. A bird, which has not this model, could record it, if it is
a member of a flock in which at least one bird has this model.
However, if a bird, which has not yet the navigation map, has technical
problems in flight, it could be lost. Examples are known of migratory birds,
which having technical flight-problems, were eventually taken into care by
people. After healing, they did not want to leave anymore. The theory
explains this by the fact that without a map and their position on the map,
they don't know where to go. However, if they see a flock in flight, they
might follow that flock.
There is a situation reported by the media, when a whole flock lost its
navigation map and remained stranded. In this situation, a plane resembling a
bird was used to guide the flock.