The evolutionary, ecological and behavioural consequences of the presence of floaters in bird populations

In spite of the huge potential impact of floaters on population processes, their biology remains poorly understood. This review, based on ornithological literature, highlights the need for a better understanding and outlines topics for future studies on the biology of floaters. The presence of floaters may be a key factor affecting sexual selection, reproductive strategies, the evolution of territoriality and population dynamics in the majority of birds. Generally, floaters have lower survival rates than territorial birds. Male and female floaters may reproduce with territorial birds, becoming helpers or nest parasites. This, however, may give rise to numerous sexual conflicts, as resident birds may copulate with floaters. It seems, though, that floating is more a contingent 'making the best of a bad job' response than an evolutionarily stable strategy. The impact of floaters encompasses numerous territorial birds because each floating individual may use much more space than the residents. As floaters exhibit greater mobility, It is possible that they may affect landscape-level processes such as patch colonization and extinction dynamics and habitat patch occupancy patterns. As yet, little is known regarding how the presence of floaters affects population survival rates and hence, population regulation. This may be of particular significance in the case of endangered species.