Predictors of aggressive response towards simulated intruders depend on context and sex in Crimson Finches (Neochmia phaeton).

Quantifying differences in aggressive behaviour across contexts can be useful in developing an understanding of life histories and breeding systems, as well as the relative costs and benefits of such behaviour. We investigated whether age, relative body size and colouration, sex, and breeding stage influenced levels of aggressive behaviour in two contexts, towards conspecific and heterospecific intruders (mounts) around active nests of group living Crimson Finches (Neochmia phaeton). We found that when responding to a conspecific mount, relative body size, and age were important in predicting the aggressive response of males toward a conspecific, with older males and those close in size to their opponent showing a higher aggressive response.