Crows are omnivorous birds that feed on a wide range of natural and anthropogenic food sources. Consequently, they can cause considerable damage to crops and livestock feed; they also engage in garbage scavenging. The distribution of crow damage in environments with multiple fruits and vegetables is uneven, indicating potential food preferences. Although an understanding of food preferences is important for efforts to predict and mitigate the costs of damage caused by wild crows, few studies have investigated this phenomenon. We investigated the relationships between food preferences and foraging behaviors of wild-caught large-billed crows (Corvus macrorhynchos) through two experiments. Dry pet food for dogs (corn, meat powder, oils, and fats) and dried corn were used as favorable and less favorable experimental food types, respectively, based on previous field observations. In the first experiment, two feeding sites, each containing one of the food types, were placed at opposite ends of an outdoor U-shaped experimental cage (i.e., two-choice trial). In the second experiment, a single feeding site was established containing either pet food or dried corn (i.e., no-choice trial). Crows were placed in individual cages in both experiments. When both food types were available, large-billed crows foraged significantly more pet food than corn. There was no significant difference in consumption when either food type was presented alone, but total foraging duration was significantly longer for corn than for pet food. These results suggested that the amount of food consumed and foraging efficiency are good indicators of food preferences in large-billed crows under captive feeding conditions. Using this experimental approach, further studies are required to investigate the preferences of large-billed crows for a variety of food items, which will help to predict damage, improve trapping efficacy, and develop effective mitigation strategies.

In Japan, the jungle crow (Corvus macrorhynchos) is a common problematic bird, causing significant economic damage. Previous attempts to mitigate conflict between crows and humans have generally been unsuccessful. Furthermore, it is not clear whether successful mitigation outcomes can be attributed to the effectiveness of control techniques. To directly examine the sensitivity of wild-caught jungle crows to a control technique, we observed their foraging behavior when auditory stimuli were applied to a single feeding patch (no-choice trial) or to one feeding patch but not the other (two-choice trial) in an outdoor cage. The auditory stimulus consisted of a low tone in the crow’s audible range (1 to 10 kHz), based on pink noise. In the no-choice trial, one feeding site was set up in a U-shaped experimental cage, and experiments were conducted under two conditions: 1) experimental sound presented at an 80 dB sound pressure level and 2) silence (i.e., control). In the two-choice trial, feeding sites were set up at both ends of the cage, and the auditory stimulus was presented at a sound pressure of 80 dB at only one of the feeding sites. All experiments were conducted with one individual at a time. The results of the no-choice trial showed that in the sound condition, as well as in the silent condition, all individuals started foraging in the presence of the sound, and there was no clear difference in foraging behavior between the two conditions presented. However, in the two-choice trial, the amount of food foraged in the feeding area under the silent condition was significantly higher than that in the feeding area under low-tone stimulus conditions. Our results suggest that jungle crows have relatively high noise tolerance; however, auditory stimulus is effective when an alternative foraging site is available. Further development of more complex experiments in captivity will elucidate the effectiveness of bird control techniques

Heron streamers/droppings, which are electrical conductors, have caused power outages at electrical substations and transmission towers. It is necessary to understand the effectiveness of techniques for scaring herons to prevent electrical outages caused by their streamers. Here, we focused on bird-management techniques using visual deterrents and evaluated the deterrent effects of light-emitting diodes (LED), lasers, and a robotic approach. Grey herons were observed on the outdoor steel structure of the High Power Testing Laboratory of the Central Research Institute of the Electric Power Industry in Yokosuka, before and after dawn. LED lights were attached to the uppermost steel structure of the laboratory to evaluate the deterrent effects. A green laser was installed 60 m north of the steel structure. The lights and laser were fired manually when herons landed on the steel structure and we evaluated the response of the birds to the stimuli. We also installed a commercial mobile robot, which was programmed to move underneath the steel structure after dawn. To investigate the deterrent effect of the size of the robot, we put a scarecrow on the robot and compared the proportions of herons deterred by the robot with and without the scarecrow. Both the LED and laser were effective before dawn, but their deterrent effects decreased significantly as the ambient illuminance increased. In the robot experiment, more than 78% of the herons were deterred from the steel structure when the scarecrow was attached, while less than 6% of the herons were deterred when we used the robot without the scarecrow. Our findings suggest the effectiveness of visual scaring techniques for herons. Bird-management strategies combining LED, lasers, and robots may be useful for deterring herons during both the day and night.