Article and images by Dr Julie O'Connor, senior conservation partnerships officer, Sunshine Coast Council
Little brown birds abound in the avian world but they all have something unique, either physically or behaviourally, that distinguishes them from each other. Possibly none come with more unique features than the delightful little golden headed cisticola (Cisticola exilis).
Firstly, it is not always a little brown bird. In the breeding season, September-March, the male develops a breeding plumage that turns the head, throat and breast a golden colour. Where some birds grow a longer tail during the showy breeding season, the male golden headed cisticola develops a shorter tail (but we will come back to this). In winter, the male plumage again loses the golden hue around the head and it reverts to a streaked crown.
The nest of a cisticola is a work of art constructed by both sexes. The rounded nest is stitched together using living grass and often additional leaves and plant debris for camouflage. It is possibly no surprise then that this little bird has also been known as the tailorbird.
Researches investigating the costs and benefits of reduced tail size in breeding males came up with some interesting findings. The researchers suggest that aerodynamic theory predicts that a short tail will improve flight performance at high speed but reduce it at low speed. In a series of experiments, artifically shortening the tails of male golden headed cisticolas demonstrated a dramatic increase in reproductive success measured as either number of chicks fledged in his territory or the number of females nesting. But while the shortened tail enhanced reproductive success there were also documented costs. As predicted, the same shorted tail was found to reduce aerodynamic performance on slow speed foraging flights. With their enhanced aerodynamic skills, short tailed males spent more time engaging in high speed flight impressing females and chasing rivals from valuable territories. Thus, researchers concluded that tail shortening is probably driven by both competition between males and the sexual selection of a mate by the females.
Once a common inhabitant of grasslands and wetlands, the golden headed cisticola is under pressure in many urban environments that typically fail to retain much of that type of habitat. However, where suitable habitat exists in the Sunshine Coast area, the golden-headed cisticola can still be found. Just listen for their distinctive calls, ranging from a musical 'teewip' or the more consistent metallic buzzing interspersed with high pitched 'tizzzeip' and 'wheezz, whit-whit'. The call descriptions might be hard to imagine on paper, but if you take a walk around the lake at the University of the Sunshine Coast, you won't be able to miss the sound of these beautiful little birds.
- Andrew Balmford, Milton J. Lewis, M. de L. Brooke, Adrian L. R. Thomas and C. N. Johnson, 2000, “Experimental analyses of sexual and natural selection on short tails in a polygynous warbler”, The Royal Society
- The Michael Morcombe & David Stewart eGuide to Australian Birds.