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Islands have always provided ideal natural laboratories for assessing ecological parameters influencing behaviour. One hypothesis that lends itself well to testing in island habitats suggests that animals frequenting highly variable environments should be motivated to approach and interact with (i.e. explore) novelty. Intra-species comparisons of populations living in ecologically different island habitats may, thus, help reveal the factors that modulate animals' responses to novelty. In this study, we presented novel objects to two geographically isolated breeding populations of the black-faced sheathbill (Chionis minor), a sedentary land-based bird that frequents remote sub-Antarctic islands. In the first population (Chionis minor ssp. crozettensis), the "Crozet group" (Baie du Marin, Ile de la Possession, Crozet Islands), breeding pairs inhabit a variable habitat close to penguin (Aptenodytes patagonicus) colonies. In the second population (Chionis minor ssp. minor), the "Kerguelen group" (île Verte, Morbihan gulf, Kerguelen Islands) breeding pairs live in penguin-free territories. In this latter population, the environment is less variable due to the presence of a broad intertidal zone which ensures year-round food availability. At both Kerguelen and Crozet, at least one breeding partner in all pairs approached at least one of the novel objects, and we found no significant differences in the latency of approach between the two populations. However, sheathbills at Crozet touched objects significantly more than birds at Kerguelen, and were also faster to touch them. We discuss how environmental variability, along with other potential influencing factors, may favour exploration of novelty in this wild insular bird., (© 2024. The Author(s).)

The capacity to follow human cues provides animals with information about the environment and can hence offer obvious adaptive benefits. Most studies carried out so far, however, have been on captive animals with previous experience with humans. Further comparative investigation is needed to properly assess the factors driving the emergence of this capacity under natural conditions, especially in species that do not have longstanding interactions with humans. Wild brown skuas (Catharacta antarctica ssp. lonnbergi) are non-neophobic seabirds that live in human-free habitats. In test 1, we assessed this species' capacity to use human behavioural cues (i.e., pecking at the same object previously picked up and lifted by a human experimenter) when the items presented were food objects: anthropogenic objects (wrapped muffins) and natural-food-resembling objects (plaster eggs). In test 2, we examined the response of another skua population towards non-food objects (sponges). Although all skuas in test 1 pecked at the objects, they pecked significantly more at the same previously handled items when they resembled natural food (plaster eggs). Most skuas in test 2, however, did not approach or peck at the non-food objects presented. Our results lead us to suggest that the use of human behavioural cues may be influenced by skuas' foraging ecology, which paves the way to further field studies assessing whether this capacity is directed specifically towards food objects and/or develops after previous interaction with humans., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Among animals, the visual acuity of several predatory bird species is probably the most outstanding. This, and the ease with which visually based tasks are administered, has led researchers to predominantly use the visual modality when studying avian cognition. Some wild skua populations routinely use acoustic cues emitted by their prey during foraging. In this study, we thus assessed whether this species was able to locate hidden food using acoustic cues alone (training phase). During the subsequent test phase, we investigated the capacity of successful individuals to choose the correct baited container in four conditions: (i) baited (shaking the baited container), (ii) full information (shaking both containers), (iii) exclusion (shaking the empty container), and (iv) control (shaking neither container). Four out of ten subjects succeeded in locating the baited container in the training phase. During the test phase, most subjects chose the baited container significantly more than the empty container in the baited and full information condition, while their performance was at chance level in the control condition. When no sound emanated from the empty container in the exclusion condition, one out of four skuas chose the baited container with more accuracy than predicted by chance. As this bird chose correctly on the first trial and during the first five trials, its performance is unlikely due to learning processes (learning to exclude the empty container). Although further tests are necessary to draw firm conclusions, our results open the way for assessing further this species' reasoning abilities in the wild., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Inferential reasoning by exclusion allows responding adaptively to various environmental stimuli when confronted with inconsistent or partial information. In the experimental context, this mechanism involves selecting correctly between an empty option and a potentially rewarded one. Recently, the increasing reports of this capacity in phylogenetically distant species have led to the assumption that reasoning by exclusion is the result of convergent evolution. Within one largely unstudied avian order, i.e. the Charadriiformes, brown skuas (Catharacta antarctica ssp lonnbergi) are highly flexible and opportunistic predators. Behavioural flexibility, along with specific aspects of skuas' feeding ecology, may act as influencing factors in their ability to show exclusion performance. Our study aims to test whether skuas are able to choose by exclusion in a visual two-way object-choice task. Twenty-six wild birds were presented with two opaque cups, one covering a food reward. Three conditions were used: 'full information' (showing the content of both cups), 'exclusion' (showing the content of the empty cup), and 'control' (not showing any content). Skuas preferentially selected the rewarded cup in the full information and exclusion condition. The use of olfactory cues was excluded by results in the control condition. Our study opens new field investigations for testing further the cognition of this predatory seabird.

Raptors are usually considered to be mainly visually dependent, and the use of other sensory modalities has rarely been studied in these birds. Here, we investigated experimentally which senses (vision and/or olfaction) Turkey vultures (Cathartes aura) and Southern caracaras (Caracara plancus) use to find hidden food. First, two identical stainless-steel perforated balls, one containing a putrefied piece of meat and the other an odorless control, were presented to birds in binary choice experiments. Both species interacted more with the smelling ball than with the control, suggesting that they were attracted by the odor of the hidden meat. In a second experiment, individuals were accustomed to eat in one specifically colored ball (blue or green). In the test phase, the meat was hidden in the opposite color with respect to the one each bird had become accustomed to. Vultures still interacted more with the smelly ball disregarding the color, while caracaras interacted equally with the two balls. The prevalence of olfaction in Turkey vultures may partly explain why they are the first raptors to find carcasses in tropical forests. In contrast, caracaras forage on the ground opportunistically, a strategy where both olfaction and sight may be involved. Our experiments suggest that both species are able to use olfactory cues for foraging. However, olfaction could be the predominant sense in Turkey vultures while olfaction and sight could play an equivalent role in Southern caracaras.