A natural move away from home

For many of Georgia’s young birds and other wild creatures, this is the time of year when wanderlust sets in. It’s not migration, which is a regular, seasonal trek to a specific destination.

Rather, this wandering is known as dispersal, when the breeding season has ended and young creatures are seeking new territories away from where they were born. It occurs among nonmigratory as well as migratory species.

In particular, scientists use the term “natal dispersal” for the movement of a bird or animal from its birth site to a new territory where it will live and raise its own babies. It’s like our children leaving home and moving into their own places across town or some other city — a natural behavior, if life in the wild is any indication.

Nearly all young songbirds, for instance, disperse from their parents’ territories a few weeks after fledging. They leave on their own or their parents may force them to leave.

The dispersal behavior of cardinals is typical of many songbirds. A young cardinal often moves a mile or so from where it was born, although some birds have been tracked wandering as far as 100 miles before settling down. Generally, male cardinals wander farther than females. A reason probably is that males are seeking territories that provide ample food, shelter, protection and other resources conducive to successful nesting.

Females, on the other hand, may choose a male based, in part, on the quality of his territory.

Dispersal, however, can be a potentially dangerous time for creatures. As they move about, they are more vulnerable to predators such as hawks and other raptors. The advantages, however, apparently outweigh the risks. For instance, dispersal greatly reduces the chances of inbreeding with close relatives, which can increase the spread of genetic defects. Dispersal also reduces competition for limited food, shelter and other resources in an area and helps a species expand its range and population.

Birds are not the only creatures engaging in natal dispersal this time of year. Black bear mothers, for instance, encourage their young — often through threats and aggression — to move away when the offspring are about 12 to 18 months of age.

Males may even swim across rivers to find a new home. It’s a reason why a lot of reports come in this time of year about black bears wandering into neighborhoods, onto highways and other places frequented by people.

Young Eastern gray squirrels also tend to disperse in the fall.

Males, however, are more likely to leave than are females. Juvenile male squirrels may move a half-mile to 10 miles away, although some have been known to travel as far as 60 miles to find a new territory.

In the sky: The moon will be last quarter Wednesday night, rising about midnight and setting around midday, says David Dundee, astronomer with Tellus Northwest Georgia Science Museum. Venus, Mars and Saturn all set in the west about two hours after sunset. Jupiter rises out of the east about three hours after sunset. Mercury is not easily seen right now.