The size difference between sexes has led to the suggestion that the Rodrigues solitaire was not monogamous as stated by Leguat, and that this deeply religious man attributed the trait to the bird for moral reasons. It has been proposed that it was instead polygynous, and the wing-rattling behaviour described for males suggests lek-mating, where males gather for competitive mating display. However, size dimorphism does occur in some monogamous birds; most other pigeons are monogamous as well. A 2015 article proposed that males invited females into their territories as secondary mates, which would result in the resident female acting aggressively towards the newcomer. Similar behaviour is seen in species that practice resource-defence polygyny. The territories probably provided all the food the birds needed in addition to acting as breeding-areas, and there was probably intense competition for favourable territories. The fact that Rodrigues island shrank by 90% at the end of the Pleistocene may also have contributed to such competition over territories, and thereby furthered sexual dimorphism.