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The Mating System and Stability of Pairs in Kiwi Apteryx spp.
Barbara Taborsky and Michael Taborsky
Journal of Avian Biology
Vol. 30, No. 2 (Jun., 1999), pp. 143-151
Stable URL: http://www.jstor.org/stable/3677123
Page Count: 9
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Different populations of kiwi Apteryx spp. live in very different habitats and climatic conditions, and they vary greatly with regard to population densities and sex ratios. Populations also differ remarkably in their social and mating patterns. By comparing four populations, we asked whether kiwi mating systems are primarily shaped by the availability of mates as caused by different operational sex ratios ("environmental polygamy potential"), or whether they depend on the costs and benefits of desertion by either sex from parental care, especially on the limitations to desertion due to high precopulatory investment ("parental limitation"). Most kiwi have long-term partnerships and very high partner fidelity, but in one population half of all pairs split each year. This is a relatively dense population with a strongly female-biased sex ratio and a complete lack of territorial behaviour. We argue that pair stability and territoriality are related in kiwi, and that the loss of territoriality and the high divorce rate in this divergent population result from the female-biased sex ratio. Data analyses did not reveal any reproductive advantage from divorce and re-mating with a different partner in kiwi. We suggest that divorce results from the interaction of surplus females with paired males and is hence "forced" upon the pair. Our analyses of social systems of the four populations of kiwi suggest that both territory defence and the degree of polygamy depend primarily on parental demands and not on the distribution of resources and mates. Hence, we regard the "parental limitation hypothesis" as being the more adequate one to explain mating patterns in kiwi.
Journal of Avian Biology © 1999 Nordic Society Oikos