The seasonal migration of wildlife is a spectacular and variable undertaking that includes epic long-distance journeys or localized movements from high to lower elevations. Driven by factors such as food availability, climate changes, or reproductive activities, these bi-annual treks involve birds, mammals, dragonflies, butterflies, and other creatures.

The migrational driver is often based upon food availability, especially for insectivorous species such as flycatchers, swifts, swallows, and shorebirds that took advantage of this summer bounty but move before the onset of winter eliminates this food resource.
Birds that have spent the breeding season in northern latitudes may be the most noticeable as they wing their way southward. Having raised their young in boreal forests, arctic tundra, or even in the local canyons around Moab, these birds leave their summer homes and head south to their wintering grounds in southern states, Mexico, or Central and South America. Some journeys are epic undertakings where birds fly thousands of miles or where the adults, such as least and western sandpipers, leave first, followed later by the young who are hardwired with directions.
Neotropical migrants is a term which describes many of the songbirds such as warblers, grosbeaks, tanagers, and other species that summer north of the US-Mexico border, but winter in neotropical habitats south of the border. It doesn’t take long to notice the decline of these species during daily birding jaunts indicates that they are on the move southward.
Some of these birds migrate at night to avoid predators and use the daylight hours to feed and rest. One very cool resource to view data about these migratory birds is on a website: Motus.org

Motus which means “movement” is a network of recording stations that include antennae and data recorders that pick up and record signals in real time from birds that have been outfitted with a small transmitter which may weight about two or three percent of the bird’s weight. These transmitters emit a morse-code like signal which identifies an individual species. There are several stations in southeastern Utah which are active and which can be viewed online.
If you’re looking to actively view migrating species, the La Sal mountains or the Matheson Wetlands Preserve are two good options to observe migrating species, especially raptors, songbirds, and waterfowl. A viewpoint on the north end of the La Sals, near Fisher Mesa, is a nice spot to watch for birds of prey rising upwards on thermals before passing along the mountain peaks or to catch the antics of Steller’s and Western scrub jays as they cache acorns for the winter ahead.
The wetlands is a better spot to look for migrating waterfowl, shorebirds, and songbirds, and perhaps some common green darner dragonflies or monarch butterflies that are also on the move. 
Also noticeable are the seasonal movements of deer and elk that have a more localized migration, mainly from the mountains downward in elevation to sagebrush flats, agricultural fields, or pinyon-juniper woodlands. Though these animals may not migrate far in terms of distance, they do gather together in herds for the fall rut. Amazingly, the mountain goats that were transplanted in the La Sals years ago mostly remain in their craggy haunts during winter, with the occasional individual wandering out of the mountains.
September is an excellent time of year to watch for wildlife in the Canyon Country, especially those species that are on the move to their wintering grounds. The Utah Division of Wildlife Resources offers some information on watchable wildlife on their website; wildlife.utah.gov, and this is a good resource to check for hunting season information which may coincide with some of this seasonal movement. Be safe and enjoy the wildlife viewing!