| Abstract: | I investigated whether plumage features are sufficient for species recognition in two sibling sympatric raptor species: the Montagu's harrier Circus pygargus and the hen harrier C. cyaneus . These species are similar in body size and differ slightly in plumage. During prelaying and laying periods, I placed artificial models close to nests of both species, simulating a conspecific male harrier (male of the same species), a heterospecific male harrier (male of the other species) or a wood pigeon Columba palumbus (acting as a control of the same size and colour). All of them represented birds perched in a neutral posture, so that they could only be recognised by their plumage differences. The use of plumage traits during this period would be particularly relevant in discriminating between their own and other species, offering the opportunity to avoid unnecessary fights, and therefore maximising the benefits of defence. I measured male responsiveness by recording aggressive behaviour towards each model (aggressive rate and time spent close to the female). Male presence time was significantly longer during conspecific decoy presentation than during heterospecific decoy presentation. Furthermore, males of both species were more aggressive towards the conspecific decoy than towards the heterospecific one, and no attacks towards the control were recorded. These results provide evidence that these birds are able to recognise plumage features of their own and the sibling species. |
