Successive nest building and polygyny of Fan-tailed Warblers Cisticola juncidis

The polygynous mating system of the Fan-tailed Warbler Cisticola juqcidis was investigated between 1978 and 1981. The male warbler builds many nests unaided; however, he has no more than one active vacant nest for courting at any time. Nest building lasted from April until August. After completing the outer fabric of a nest, the male advertised it and led a female to the nest site by a unique invitation flight. On average a male built 6.5 nests during one breeding season and three of them were accepted by females. The most successful male completed 18 nests, and mated with 11 females. Out of a total of 111 males which established a territory, 30 had no mate, 14 were monogamous, and the rest were polygynous. About 50 to 70% males were polygynous over the four years. The sex ratio varied from 1.41:1 to 2.17:1 (females: male) in the breeding population. It was partly caused by the presence of 'floating males'. After the completion of the outer fabric of the nest, the male warbler did not take any further role in nesting and caring for young.
The polygynous mating system of the Fan-tailed Warbler is characterized by successive nest building. Its extreme development results from the long breeding period and the male having no role in parental care.