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Homing pigeons (Columba livia) were trained to locate a goal in one comer of a rectangular arena by either its shape (geometry) or the left-right configuration of colored features located in each comer (feature structure). Control and hippocampal-lesioned pigeons learned at a similar rate, but the control birds made proportionally more geometric errors during acquisition. On conflict probe trials, the control birds preferred geometrically correct comers, whereas the hippocampal-lesioned birds displayed a greater preference for the correct comer defined by feature structure. On geometry-only probe trials, both groups demonstrated an ability to identify the goal location. Hippocampal lesions do not interfere with goal recognition by the feature structure of local cues but diminish the salience of arena shape. Keywords: hippocampus, pigeons, geometry, structure, space

Homing pigeon breeds, the product of artificial selection on the basis of navigational and spatial ability, differ from nonhoming breeds in hippocampal size and distribution of N-methyl-D-aspartate (NMDA) dependent receptors. The effects of MK-801 (0.1 mg/kg administered intraperitoneally), a noncompetitive NMDA antagonist, on spatial reference memory (RM) were compared between the 2 breeds in a radial arm maze task. MK-801 disrupted the acquisition of RM in the nonhoming group but not the homing group, which was equivalent to the 2 saline-only control groups. As in previous findings with mammals, working memory was not affected by MK-801. This behavioral dissociation, coupled with differences in NMDA-dependent long-term potentiation between breeds, suggests an exceptional opportunity to investigate the role and function of the dorsomedial telencephalon region in spatial RM, through anatomical, neurochemical, and behavioral comparisons between homing and nonhoming pigeon breeds.

Young homing pigeons were subjected to hippocampal lesion before being placed in their permanent loft to examine what effect such treatment may have on the development of their navigational map, which supports homing from distant unfamiliar locations. When later released from 3 distant unfamiliar locations, the hippocampal-lesioned pigeons were impaired in taking up a homeward bearing. The results identify a deficit in the acquisition of navigational ability after hippocampal ablation in homing pigeons. The results strongly suggest a deficit in navigational map acquisition, but alternative interpretations cannot be excluded. The findings offer the first insight into the central neural structures involved in the acquisition of the pigeon navigational map. Further, the results identify the hippocampus as a structure critical for the regulation of navigational behavior that manifests itself in a natural setting.

Homing pigeons and other birds can sense the Earth's magnetic field, an ability that helps them find their way home, even when home is hundreds of miles away. But how […]