Red-backed fairy-wren

Article and images by Dr Julie O'Connor, senior conservation partnerships officer, Sunshine Coast Council

In the non-breeding season male red-backed fairy-wrens are almost identical to females, with brown above and fading to whitish below. But in the breeding season, the dominant male is unmistakable in his bright red or orange-red saddle over glossy black body and tail feathers.

Red-backed fairy-wrens are socially monogamous but sexually promiscuous. That is, a breeding pair form a close bond and are strongly territorial, yet extra-pair paternity is common. One might think that this would lead to increased aggression from the dominant male. But, apparently the male red-backed fairy-wren is more of a lover than a fighter. Researchers found that males who sang a duet with their mate in the presence of intruders had higher rates of paternity than those who did not.

The trill song of the red-backed fairy-wren has also long been appreciated by bird lovers. In September 1937, a writer to the Central Queensland Herald penned:

…Loud in the fragrant orchard the lark and whistler sing, And cuckoos quaint, ascending notes proclaim the vibrant Spring. Gay rainbow birds are flashing through sunlit heights again, And sweetly falls upon the air, the song of a red-backed wren.

In beauty of black and crimson, ’mid the oleander blooms, He sings to his mate, and fledglings, clad in modest russet plumes. They perch so still and friendly, there rises in my breast A wish to find and contemplate the little cock-tail’s nest…

Red-backed fairy-wrens may have developed a strategy to outwit brood parasites, such as the Horsfield bronze-cuckoo. From the fifth day of incubation, the female fairy-wren will sing a distinctive and unique tune to her eggs every few minutes. When the chicks hatch, they incorporate the learned signature notes into their begging calls, which are readily recognised by the parents. In this way they have effectively created a “vocal password” that identifies them as the fairy-wrens’ own young. Scientists tested whether this was a learned or an innate ability by swapping clutches in 22 different nests to see whether the nestlings would adopt the calls of their biological mother or those of their foster mother. The young chicks were found to adopt the calls of their foster mothers, thus validating the embryonic learning theory.

A study by some of the same researchers found that effective vocal imitation of the mother’s calls resulted in increased parental provisioning for young nestlings. So, it could be that the use of embryonic teaching and learning to distinguish fairy-wren nestlings from cuckoo interlopers might just be a happy coincidence.

References:

• Ackerman, J. (2021). The Bird Way: A New Look at How Birds Talk, Work, Play, Parent, and Think. Penguin
• Baldassarre, D. T., Greig, E. I., & Webster, M. S. (2016). The couple that sings together stays together: duetting, aggression and extra-pair paternity in a promiscuous bird species. Biology letters, 12(2), 20151025
• Colombelli-Négrel, D., Webster, M. S., Dowling, J. L., Hauber, M. E., & Kleindorfer, S. (2016). Vocal imitation of mother's calls by begging Red-backed Fairywren nestlings increases parental provisioning. The Auk: Ornithological Advances, 133(2), 273-285
• Dowling, J. L., Colombelli-Négrel, D., & Webster, M. S. (2016). Kin signatures learned in the egg? Red-backed fairy-wren songs are similar to their mother's in-nest calls and songs. Frontiers in Ecology and Evolution, 4, 48.