Bait fishing is a behaviour described in only 12 species of birds, seven of which belong to the family Ardeidae (herons), the remaining five are scattered among four other bird families. This behaviour is defined as having the following characteristics: (1) Objects placed by the bait fisher on the water are buoyant and within a radius at which the fisher can strike at prey. (2) The objects attract or distract the fisher’s prey, with the effect that the fisher enhances its chances of prey capture. A review of the literature indicates that bait items are both selected from and placed within the environment to achieve enhanced prey capture success. It is concluded that bait fishing is a real and distinctive behaviour. The evolutionary route to bait fishing has most likely been through an association between particular floating objects and the occurrence of fish prey. The repositioning of these floating objects and the collection of objects of similar character would have then been sufficient to achieve the bait fishing behaviour now seen. Bait fishing falls within a commonly used definition of tool use. However, it is argued that, as with tool use and tool making in general, this does not necessarily imply special cognitive ability. The rare occurrence of bait fishing both within and across species as could be an indication of cognitive constraint; but this remains undemonstrated. Alternatively, this rarity could be explained if fishing is rarely more profitable than alternative foraging tactics.