With the breeding season over for most bird species, young birds that have fledged their nests are striking out on their own. Where will they go? Many of them will seek nesting territories of their own, away from their birthplaces — probably the reason why many birds engage in a kind of wanderlust at this time of year.
It’s not migration, which is a regular, seasonal trek to a specific destination. Rather, this phenomenon is called “post-breeding dispersal,” when young, first-year birds and some adults that have finished breeding seem to aimlessly wander around. It occurs among nonmigratory as well as migratory species, which may roam around before finally heading south for the winter.
Ornithologists believe there is a method to what seems like purposeless rambling: The birds may be seeking new areas in which to set up territories next spring, away from where they were born. When nesting season commences in spring, they will return to these areas — instead of their birthplaces — to set up their own little domains where they will live and raise their own babies.
In a way, it’s like our children leaving home and moving into their own places across town or in another city. In the wild, young birds leave on their own or their parents may force them to leave.
The scientists believe that post-breeding dispersal, also known as “natal dispersal,” may be nature’s way of reducing competition for food and mates and preventing inbreeding among close relatives. It also may be a way for offspring to locate new resources and establish new populations to ensure survival of their species.
The dispersal pattern of Northern cardinals is typical of many songbirds. A young cardinal may disperse two weeks after hatching and move a mile or more from where it was born. 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. A female may accept a male suitor based on the quality of his territory.
IN THE SKY: From David Dundee, Tellus Museum astronomer: The moon will be new on Sunday. Mercury and Venus are low in the west around dusk; Venus will appear near the moon on Monday evening. Mars and Jupiter rise in the east about four hours before sunrise. Saturn rises in the east just after dark.
Charles Seabrook can be reached at charles.seabrook@yahoo.com.
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