Different populations of kiwi Apteryx spp.
Populations also differ remarkably in their social and mating patterns.
By compar 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. 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.