The role of birds in the acacia—ant interaction: New insights from nest predation

Abstract

The association of the swollen-thorn acacia (Acacia cornigera) and ants is an example of defensive mutualism. It has been shown that some bird species prefer to nest in myrmecophyte acacias, suggesting that their nests are protected from predators by the associated ants. Based on previous knowledge regarding the existence of extended benefits for birds in the acacia-ant interaction, the role of the rufous-naped wren was analyzed within the ant-acacia system. Nest predation was assessed taking into account tree species with and without myrmecophytic interactions, tree cover and height, the presence and abundance of ants, predator type, and the distance between each nest and the closest myrmecophyte acacia. The probability of survivorship of artificial nests using a known fate analysis was calculated. The results showed non-significant differences in the probability of survivorship regardless of the presence and density of myrmecophyte acacias, tree cover and height, the presence and abundance of ants, or predator type. Interestingly, the highest degree of predation in the artificial nests was related to the rufous-naped wren. These results suggest that the acacia-ant-bird interaction is more complex than previously perceived.