Patch choice decisions of wild blackbirds: the role of preharvest public information

Although group foragers have the potential to enhance their patch choice de cisions by observing the sampling behaviour of competitors (i.e. using 'pub lic information'), empirical support for such an ability is sparse and conf licting. We examined whether wild blackbirds, Turdus merula, were more like ly to choose the richer (20-fold) of two seminatural food patches if they h ad seen other blackbirds (demonstrators) feeding in them beforehand. There was no evidence that birds having such preharvest public information prefer entially selected the richer patch, even if their choice was not limited by the continuing presence of dominant demonstrators. Nor did patch selectors favour the patch occupied by a demonstrator (or just vacated by one) despi te an above-average probability that these patches were the richer. Instead , our birds often showed preferences for one or other of the otherwise iden tical patch locations, were more likely to select the rich patch if it had not changed location since their last visit, and avoided dominant conspecif ics. We conclude that preharvest public information has little or no influe nce on blackbird patch choice decisions. (C) 2001 The Association for the S tudy of Animal Behaviour.