A report on a characteristic vocalization in Corvus macrorhynchos osai with an indication of vocal learning

In the process of vocal learning, animals give immature vocalization, such as babbling and subsong. Here I report a characteristic vocalization given by a subspecies of large-billed crow, Corvus macrorhynchos osai, that live in Kuroshima Island, Okinawa, Japan. This vocalization (type-K) is characterized by very rapid bill movements (ca. 13 times/sec). The type-K was heard throughout the island, indicating that the population of the Kuroshima Island share this call type. In addition, a juvenile crow was observed giving immature type-K repeatedly. This observation suggests that this call type is not innate but acquired through vocal learning.

Humans Discriminate Individual Large-Billed Crows by their Calls

Previous research has shown that humans can discriminate two individual rhesus monkeys (Macaca mulatta), as well as two individual zebra finches (Taeniopygia guttata) by their vocalizations. The discrimination of individual zebra finches largely relies on differences in pitch contour, although this is not the only relevant cue. The purpose of the present experiment was to examine whether humans can also discriminate two individual large-billed crows (Corvus macrorhynchos) by their calls. Discrimination was tested with a forced-choice Same-Different Paradigm. Results show a high discrimination accuracy without prior training, although the scores obtained here were lower than those in the zebra finch discrimination task. There was no significant learning trend across trials. Future studies should investigate which acoustic cues participants use for the discrimination of individual crows and expand these findings with more non-human animal vocalizations.

The whole is equal to the sum of its parts: pigeons (Columba livia) and crows (Corvus macrorhynchos) do not perceive emergent configurations

We previously demonstrated that chimpanzees, like humans, showed better accuracy and faster response time in discriminating visual patterns when the patterns were presented in redundant and uninformative contexts than when they were presented alone. In the present study, we examined the effect of redundant context on pattern discrimination in pigeons (Columba livia) and large-billed crows (Corvus macrorhynchos) using the same task and stimuli as those used in our previous study on chimpanzees. Birds were trained to search for an odd target among homogenous distractors. Each stimulus was presented in one of three ways: (1) alone, (2) with identical context that resulted in emergent configuration to chimpanzees (congruent context), or (3) with identical context that did not result in emergent configuration to chimpanzees (in- congruent context). In contrast to the facilitative effect of congruent contexts we previously reported in chimpanzees, the same contexts disrupted target localization performance in both pigeons and crows. These results imply that birds, unlike chimpanzees, do not perceive emergent configurations.

Attacked from above and below, new observations of cooperative and solitary predators on roosting cave bats

Predation of bats in their roosts has previously only been attributed to a limited number of species such as various raptors, owls, and snakes. However, in situations where due to over-crowding and limited roost space, some individuals may be forced to roost in suboptimal conditions, such as around the entrances of caves and may thus be vulnerable to predation by species which would normally be unlikely to predate bats whilst roosting inside caves. Here, we describe the first documented cooperative hunting of the Large-billed Crow, Corvus macrorhynchos Wagler, 1827 (Passeriformes: Corvidae) and opportunistic predation by the Yellow-headed water monitor, Varanus cumingi Martin, 1839 (Squamata: Varanidae) in the world’s largest colony of Geoffroy’s Rousette, Rousettus amplexicaudatus (É. Geoffroy Saint-Hilaire, 1810) (Chiroptera: Pteropidae) in the Island of Samal, Mindanao, Philippines.