In the Rocky Mountain region vertical migrations are particularly notable. Chickadees, rosy finches, juncos, pine grosbeaks, Williamson's sapsuckers, and western wood pewees nest at high altitudes and move down to the lower levels to spend the winter. The dark-eyed juncos breeding in the Great Smoky Mountains make a vertical migration, but other members of the species, breeding in flatter areas, make an annual north-south migration of hundreds of miles (Van Tyne and Berger 1959). There is a distinct tendency among the young of mountain-breeding birds to work down to the lower levels as soon as the nesting season is over. The sudden increases among birds in the edges of the foothills are particularly noticeable when cold spells with snow or frost occur at the higher altitudes. In the Dead Sea area of the Middle East, some birds that breed in this extremely hot desert move up into the surrounding cooler hill during the winter (Thomson 1964). The vertical migrations of some mountain dwelling gallinaceous birds (mountain quail and blue grouse) are quite interesting because the annual journey from breeding to wintering grounds is made on foot. Mountain quail make this downward trek quite early in the fall well before any snows can prevent them from reaching their goal. Blue grouse perform essentially the same journey in reverse. During midwinter, these birds can be found near timberline eating spruce buds protruding above the snow. These illustrations show that the length and direction of a migration route are adapted to the needs for survival and are met in some cases by a short vertical movement or great latitudinal travels in others. Pre-migratory Movements Recent banding studies have demonstrated many migrants, especially young of the year, have a tendency to disperse after fledging. These premigratory movements have also been called "post-fledging dispersal," "reverse migration," and "postbreeding northward migration." Demonstration of this phenomenon is especially important as it relates to locality-faithfulness (Ortstreue), range extension, and gene mixture between populations. These movements cannot be considered as true migrations even though they are repeated annually by the species between breeding grounds and some other area. These movements are generally repeated by the same age class in the population but not the same individuals.