[Relative numerousness judgements in crows and pigeons in the urgent comparison of stimuli earlier linked to different amounts of reinforcement].

The ability of pigeons (Colomba livia, L.) and crows (Corvus corone cornix, L.) was studied to realize urgent numerousness judgement of reinforcement consisting of discrete elements (wheat grains and meal worm larvae, respectively). In the process of preliminary training the birds mastered the information about the conformity of the feeder colour with the definite number (1-9 for pigeons and 5-12 for crows) of reinforcement units at isolated presentation of feeders. In test at presentation of pairs formed from these feeders, pigeons and crows chose the stimulus connected with a greater quantity of reinforcement. In the range of 1-8 units the precision of choice in pigeons depended on absolute and relative differences between comparing values. In crows in the range of 6-12 this dependence was not revealed. The ability to solve the given test is considered as one of manifestations of elementary reasoning.