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SUMMER 2005
A Bluebird’s Life
by Judy Purdy

Patricia Adair Gowaty is keeping an eye on who’s mating with whom — not just out of nosiness but to chronicle love on the wing. Specifically, the UGA evolutionary ecologist wants to know more about eastern bluebird behavior and how it affects nesting success. By delving into the family life of one of America’s most popular songbirds, she is rewriting much of this species’ natural history.

For instance, Gowaty’s team has found that “single-mom” nests are just as likely to succeed as two-parent nests. Such findings spur her to raise such questions as: Might a songbird mom actually be allowing her partner to help with chick-rearing?

The UGA team collects data at standard intervals on more than 200 bluebird pairs in Georgia and South Carolina throughout the nesting season (March through August), when they often raise as many as three broods. The researchers regularly observe behavior of bluebird moms and dads individually for 30-minute intervals, noting whether they’re incubating eggs, feeding young, or, perhaps, cleaning out the nest. The team also counts eggs, monitors chick growth, places identification bands on parents and nestlings, and takes a blood sample from each bird.

Molecular analysis of blood samples led Gowaty to publish the first paper (1984) that established extra-pair paternity — where females have more than one sexual partner — in a socially monogamous bird. In subsequent studies she showed that bluebird moms of all ages leave their territories to seek additional mating partners. Now she and her students are concentrating on how variation among bluebird mothers’ ability to raise their offspring alone affects their extra-pair mating behavior.

Some of Gowaty’s other findings include the following.

• Females are more likely to mate with more than one male when population density is greater.
• Single moms are just as likely as partnered moms to survive to the next breeding season, and their chicks are just as likely to return to the breeding area.
• Females tend to be more aggressive when nests are most vulnerable to being parasitized by other females looking for a place to lay eggs.
• A mom who displays neediness gets more domestic help from her partner than one who behaves competently.
• A male bluebird spends a lot of time aggressively guarding his mate during mating season.
• Dads, especially younger dads, have greater odds of caring for nestlings sired by another male if mom leaves the territory more frequently during her fertile periods.
• Fathers give no preferential parenting treatment to their own young in mixed-paternity nests.
• Bluebird couples whose bonding endures throughout the entire breeding season — the individuals remain together instead of switching mates after raising one or two families — have fewer half-sibling chicks in their nests.
• Parents who spend more time in their own territory have fewer chicks of mixed paternity.

Because Gowaty peers into the bluebird’s daily activities from both the dad’s and the mom’s perspective, “her questions are so different from what other people ask,” said UGA doctoral student Jason Lang, who coordinates the UGA bluebird field research. That approach has helped her attract international attention and earn recognition from her peers. Gowaty holds a lifetime appointment on the governing body of the International Ornithological Congress and has received a North American Bluebird Society research award. She also is a Fellow of the American Ornithologists’ Union, the Animal Behavior Society and the American Association for the Advancement of Science.