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Breeding behaviour and ecology of the sexually size-dimorphic brown songlark, Cinclorhamphus cruralis

Magrath, M. J. L., Brouwer, L., Petersen, A. V., Berg, M. L. & Komdeur, J., 2003, In : Australian Journal of Zoology. 51, 5, p. 429-441 13 p.

Research output: Contribution to journalArticleAcademicpeer-review

The Australian endemic brown songlark, Cinclorhamphus cruralis, is one of the most sexually size-dimorphic of all birds, and yet its breeding ecology remains poorly documented. Here we redress this situation by describing the breeding activities of brown songlarks over three years ( 1998 - 2000) in the semi-arid grasslands of south-western New South Wales. Study populations of this nomadic species were selected in late August of each year on the basis of high adult abundance. Adult males at these sites were, on average, 2.3 times heavier than females. Over the three seasons, nesting activities started in early to late August and continued until early November or December. Males were highly polygynous and, on average, occupied territories of about 4.0 ha. Nests were well concealed at the base of small shrubs and grass tussocks or in thick herbage. Clutches ranged in size from 2 to 5 eggs ( mean 3.2) and were incubated exclusively by the female for 11 - 13 days ( mean 12.1). Nestlings received a range of invertebrate prey, mainly from the female, for 10 - 14 days ( mean 11.5) before leaving the nest. Only 17% of nesting attempts were estimated to be successful, and each of these nests produced an average of 2.7 fledglings. Predators, including foxes, Vulpes vulpes, and brown snakes, Pseudonaja textilis, were the main cause of nest failure. Some females produced replacement clutches following nest failure, while others laid second clutches after the success of an earlier brood. We speculate that extreme size dimorphism has evolved in this species because (i) males compete physically for breeding territories, and (ii) habitat heterogeneity and excellent visibility of their surroundings allow some males to defend territories of sufficient size to support nesting by multiple females.

Original languageEnglish
Pages (from-to)429-441
Number of pages13
JournalAustralian Journal of Zoology
Volume51
Issue number5
Publication statusPublished - 2003

    Keywords

  • BIRDS, EVOLUTION, SEX, DNA

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