Of course, some birds do not head for warmer areas in the winter. This seemed to divid birds quite nicely into two categories: migratory and non-migratory (i.e., resident) birds.
Heape (Emigration, migration and nomadism, 1931, Cambridge: Cambridge University Press) tried to find other animals tht migrate like birds (i.e., were "true migrants"). At this point in time some animals, including some fish and whales, were accepted as migratory. The rest were, like resident birds, classed as non-migratory. Heape noticed that some animals that were classed as non-migrant, however, showed intriguing movements that required further sub-division of the terminology. He proposed the terms nomadism and emigration.
Nomadism described animals that appeared to wander about without returning copnsistently to the same location at the same time each year. Emigration implied movement away from unsuitable conditions. It was soon noticed that such movement usually produced colonizers as well as refugees. For the latter, the term emigration was inadequate. Subsequently, the term dispersal, was adopted because emigration had usually been applied to situations in which animals scattered in all directions from their place of origin. Unfortunately, as time would demonstrate, this was an even worse choice of terminology that the inadequate term of emigration.
Mammologists were the first to adopt ther term dispersal wholeheartedly. They used the term to describe the behaviour of young mammals that abandoned the area they were born in to settle elsewhere. Ornithologists also adopted the term dispersal for a similar behaviour: the movement of just fledged birds away from the nest. However, the term quickly came to be used by both mammologists and ornithologists to describe changes in breeding sites which resulted in the segregation of previously cohesive breeding groups. By the 1960s all non-trivial movement was either described as migration, dispersal, or nomadism. In other words, anything that wasn't migration or nomadism was dispersal. The original meaning of the term was quickly forgotten and it was subsequently used in a variety of semantic corruptions.
The verb "scatter" means "to disperse". It applies to groups of things leaving an area. However, it was quickly, and inappropriately, applied to individuals. The onlyway an individual can, technically, scatter is...messy.
Entomologists of the 1950s saw insect migration as directed and as involving back and forth seasonal reversals. In the late 1960s an argument arose in the entomological community against directed insect movements and what had previously been defined as migration was now termed dispersal by the school of thought championed by C.G Johnson (1969). In fact, all non-trivial insect movements were now called dispersal, with a total disregard for the original meaning of the word. The final corruption came when the convergence of some insects upon hibernation sites in vast numbers was included under the general term of dispersal.
Johnson subsequently redefined migration and dispersal as being synonymous, calling migration "the adaptive change of breeding habitat". OF course, this was pretty much the same definition mammologists and ornithologists used for the term dispersal! By 1970 mammologists and ornithologists defined migration as the to-and-fro return movement that ended where it began (i.e., at the original breeding site). Entomologists used the term in exactly the opposite sense: to indicate on change in breeding sites.
Completely segregated from this terminological discussion where the demographers, anthropologists, and social scientists who were attempting to develop their own terminology independently. Quite by chance they ended up allying themselves with entomologists, rather than with those groups who studied other vertebrate groups. Researchers dealing with human movement tended to use migration and dispersal interchangeably, but the emphasis was slightly different from how entomologists used the terms. While entomologists said migration was really dispersal, human demographers said that dispersal is really migration. As a final twist, humans that performed seasonal return migrations, comparable to similar feats performed by birds, were not classifed as migrants, but as nomads!
Behaviourists, championed by American psychologists like Watson and Skinner, maintained that animals migrate/navigate through a series of learned behaviours. Internal programs or drives were considered irrelevant. It was the early learning patterns that were seen as being extremely influential in determining how animals migrate. Observational learning is seen to play a major role, especially the observation of parents or other experienced adults by juveniles. The radical behaviourist star (e.g., Watson and Skinner's approach that argues against making any inferential judgements) has waned with the cognitive revolution of the 1970s. Nevertheless, there is still a great deal of merit in considering the impact of observational learning and reinforcement schedules when considering many questions of short and medium range navigation (this is especially true for certain social birds and mammal species).
Behavioural ecologists (e.g., R. Robin Baker) and sociobiologists (e.g., E.O. Wilson) are a third group of researchers who have recently become invovled in the study of navigation and migration. Behavioural ecology truly come into its own through the late 1970s and early 1980s. Generally, behaviural ecologists are interested in animal behaviours that serve to increase the reproductive fitness of a species. However, at the level of the individual behavioural ecologists maintain that animals are individuals confronted with dangers and problems that must be sovled if they are to survive and reproduce. Behavioural ecologists agree that animals come equipped with genetic predispositions (as argued for by ethologists) and are more than capable of learning through conditioning (as argued for by behaviourists). Social scientists argue that man is a sentient creature. Behavioural ecologists suggest that there is no good reason for assuming this feature is unique to humans, and maintain that all animals are, to greater or lesser degree, sentient. Animals are individuals, packed with predispositions and learned experiences. They are the produce of natural selection and are sentient creatures prepared to solve any problem a complex environment can throw at them, or die in the attempt.
Kinesis involves movement in a random direction. A stimulus (e.g., light, moisture, temperature) occurs and the animal begins moving. When the stimulus is removed the animal stops moving. It is important to remember that kinesis is not directed movement. That is, the animal isn't moving towards or away from something, it is just moving. It will continue moving until the motivating stimulus is no longer present.
Taxis involves directed movement. That is, movement that bears some relationship to the location of a stimulus. In this case, in the presence of a stimulus the animal proceeds to move either towards or away from the source of the stimulus. Chaoborous, for example, are freshwater larval stages of midges. They demonstrate verticle movement up and down in the water column due primarily to light levels: In the presence of light they move up through the water column, without light they move down.
Depending on who you talk to, trophisms may or may not be viewed as simple forms of navigation. I am inclined to call trophisms orientation responses. As such, they may be considered the minimum requirement for a navigating organism.