Species recognition without early experience: brush turkey chicks use visual cues to aggregate with conspecifics

One of the fundamental problems in the study of behavioural development is understanding the mechanisms by which animals recognize conspecifics. Species recognition is important because it ensures short-term survival and influences mate choice decisions in adulthood. In most birds and mammals, offspring initially associate with their parents; early experience thus plays a critical role. But one remarkable group of Australian birds, the megapods, reveals that other developmental pathways can evolve: chicks do not meet their parents after hatching and thus have no opportunity to learn from them. Here we describe recent work on species recognition in chicks of the Australian brush-turkey Alectura Lathami. Simultaneous choice experiments using taxidermically-prepared robots presented under optical filters show that socially-naive hatchlings prefer to approach conspecifics of similar colour and that short wavelengths are responsible for this effect. In addition, chicks prefer moving robots to static ones, and pecking movements to a control in which the head sweeps from side to side. Morphology and behaviour hence act synergistically to account for the aggregation response. We discuss the implication of these results for the current debate concerning species recognition and speciation. In northern Queensland, two megapode species (the brush-turkey and the Orange-footed megapode Megapodius reinwardt) occur sympatrically and incubate their eggs in the same incubation mounds. Chicks look similar to the human eye. The mechanisms responsible for species recognition are thus likely to be highly specific, ensuring that no "mistakes" in mate choice are made and no interbreeding occurs.