Zugunruhe

In ethology, zugunruhe or migratory restlessness is anxious behavior in migratory animals, especially birds. These animals show this behavior even when they are confined, if they receive the environmental stimuli corresponding to one of the migration periods. The confinement of animals in special cages, for example in an Emlen funnel, makes it possible to induce zugunruhe and thus study the cycles of the migratory syndrome. Zugunruhe involves an increase in activity before and after sunset with changes in normal sleep patterns. Ethologists have been able to study the endocrine control and guidance mechanisms associated with migration studying the zugunruhe.

This term of German origin is a word composed of Zug (meaning movement or migration) and Unruhe (meaning agitation, anxiety or restlessness).

Zugunruhe has been artificially induced in experiments by simulating long days. Some studies on Zonotrichia leucophrys (white-crowned sparrow) have suggested that prolactin is involved in hyperphagia (or overeating), fattening and zugunruhe, however others have found that prolactin may only be associated with lipogenesis (fat accumulation).

It was generally thought that the phenomenon of zugunruhe was found only in migratory species, however the study of resident species shows low levels of zugunruhe, including orientation activity, suggesting that endogenous mechanisms for migratory behavior may be present even in resident species. Additional indications of the existence of endogenous programs are provided by the observations that the number of nights in which the zugunruhe is exhibited i> by caged migrants seems related to the distance involved in the migration usually carried out.