Polyandry and competition for territories in bronze‐winged jacanas

Abstract

Summary1. We tested the hypothesis that in territorial, sex‐role reversed birds the distribution of resources may determine the dispersion of males, which may, in turn, determine the dispersion of females (i.e. the converse of the classical view of breeding systems in most species).2. Bronze‐winged jacana (Metopidius indicus) territories were exclusive within the sexes, and female territories encompassed 1–4 male territories. The breeding density was limited by both habitat availability (floaters settled when new habitat flooded) and competition for territories (floaters filled natural and experimental vacancies).3. Territory vacancies created by removal experiments were filled quickly either by floaters, neighbours, or male co‐mates that expanded their territories. Changes in male territories had a significantly greater impact on female territories than vice versa, in terms of size and overlap before and after the experiment. Female dispersion was therefore influenced by the dispersion of males. However, males also played an active part in mate changes through occasional territory adjustments, and sexual interactions with females.4. There was no evidence for a relationship between dispersion of resources and male territory size, but heavier males defended larger territories. Both neighbouring males and co‐mates constrained the size of male territories. There was no evidence that polyandry arose through males settling on and subdividing female territories, but rather males competed for space, and female territories were superimposed on the mosaic of male territories.5. Female territory size was positively correlated with harem size, but seemed to be unrelated to habitat quality. Females may have attempted to maximize territory size to encompass as many males as possible. Males in larger harems defended smaller territories. The degree of polyandry therefore depended on both male and female territory sizes.