New Caledonian Crows Research Articles

Designing a novel method based on multiplex PCR for detecting various meat of birds in processed ground meat products

Falsified food directly influences wildlife, fair trade, religion, and the health of society. Here, we report a multiplex polymerase chain reaction to evaluate the accurate determination of seven species of bird meat in meals on a single assay platform. To amplify segments of DNA fromColumba livia, Corvus moneduloides, Gallus gallus, Coturnix japonica, Phasianus colchicus, Struthio camelus, and Meleagris gallopavomeats, respectively, a total of seven sets of species-specific primers targeting the mitochondrial and cytochrome b genes were developed. Gel photographs and electrochromatography from an Experion Bioanalyzer were used to identify all PCR products. Species specificity checks discovered no cross-species amplification. The applicability of its screening to find target species in processed food was shown in commercial and model meatballs. A validation study revealed that the test is reliable, quick, affordable, repeatable, specific, and accurate down to 50,000 mitochondrial copies. It might be used for raw meats and products involving processed and severely deteriorated food samples. The customers, the food business, and law enforcement would all benefit immensely from this suggested approach.

Modulation of behavioural laterality in wild New Caledonian crows (Corvus moneduloides): Vocalization, age and function

ABSTRACT The New Caledonian crow (Corvus moneduloides) is known for displaying a unique set of tool-related behaviours, with the bird’s bill acting as an individually consistently lateralized effector. However, we still fail to understand how such laterality develops, is modulated or even if its expression is consistent across other behavioural categories. Creating the first ethogram for this species allowed us to examine laterality and vocalisations in a population of wild, free-flying New Caledonian crows using detailed analyses of close-up video footage. We revealed the existence of an overall strong left-sided bias during object manipulation only and which was driven by the adult crows of our focal population, the stabilization of individual preferences occurring during the birds’ juvenile years. Individually, at least one crow showed consistent side biases to the right and left within different behavioural categories. Our findings highlight previously unknown variability in behavioural laterality in this species, thus advocating for further investigation. Specifically, we argue that a better understanding of the New Caledonian crow's biology and ecology is required if one wishes to pursue the promising comparative road that laterality could be connected to the evolution of tool-making.

Tools and food on heat lamps: pyrocognitive sparks in New Caledonian crows?

Abstract Fire has substantially altered the course of human evolution. Cooking kindled brain expansion through improved energy and time budgets. However, little is known about the origins of fire use and its cognitive underpinnings (pyrocognition). Debates on how hominins innovated cooking focus on archaeological findings, but should also be informed by the response of animals towards heat sources. Here, we report six observations on two captive New Caledonian crows (Corvus moneduloides) contacting heat lamps with tools or placing raw food on them. The tools became singed or melted and the food had browned (and was removed). These results suggest that New Caledonian crows can use tools to investigate hot objects, which extends earlier findings that they use tools to examine potential hazards (pericular tool use), and place food on a heat source as play or exploration. Further research on animals will provide novel insights into the pyrocognitive origins of early humans.

DNA barcoding identifies cryptic animal tool materials.

Some animals fashion tools or constructions out of plant materials to aid foraging, reproduction, self-maintenance, or protection. Their choice of raw materials can affect the structure and properties of the resulting artifacts, with considerable fitness consequences. Documenting animals’ material preferences is challenging, however, as manufacture behavior is often difficult to observe directly, and materials may be processed so heavily that they lack identifying features. Here, we use DNA barcoding to identify, from just a few recovered tool specimens, the plant species New Caledonian crows (Corvus moneduloides) use for crafting elaborate hooked stick tools in one of our long-term study populations. The method succeeded where extensive fieldwork using an array of conventional approaches—including targeted observations, camera traps, radio-tracking, bird-mounted video cameras, and behavioral experiments with wild and temporarily captive subjects—had failed. We believe that DNA barcoding will prove useful for investigating many other tool and construction behaviors, helping to unlock significant research potential across a wide range of study systems.

Bending and Unbending of Tools by New Caledonian Crows (Corvus Moneduloides) in a Problem-Solving Context

New Caledonian crows (NCCs) are proficient tool manufacturers and flexible problem solvers. A study reporting innovative hook bending by a captive individual in 2002 (Weir et al., 2002), has since been cited as a remarkable case of causal reasoning in animals. Recently, however, tool bending has been found to form part of the species’ natural behavioral repertoire. Yet, further studies examining the flexibility of this behavior in controlled novel problem-solving contexts are lacking. We tested 17 captive NCCs, in one tool bending and three unbending problem-solving experiments. In the first study, two groups of five subjects were trained to select inflexible straight or hooked tools respectively for retrieving food from an apparatus. In the subsequent test, the crows were supplied with the wrong, but now pliable, type of tool. Three subjects made hooks while one subject straightened tools consistently. In the second study, 13 subjects, including five from Study 1, were tested. Ten subjects received an unbending task with a Z-shaped tool without prior training. Both angles needed to be straightened for the tool to become sufficiently long for reward retrieval. Four subjects solved the task at least once, and two did so consistently. Eight subjects, including the previous solvers, were challenged with yet another apparatus, requiring novel unbending behavior. One crow succeeded in both unbending tasks consistently. Our results show that NCCs can flexibly bend or unbend pliant material to create tools for solving novel tasks. The underlying cognitive mechanisms seemingly varied across individuals although trial-and-error learning prevailed.

New Caledonian Crows and Hidden Causal Agents Revisited

A previous experiment suggested that New Caledonian crows (Corvus moneduloides; henceforth NCCs) can reason about hidden causal agents (Taylor et al., 2012). In that study, subjects showed greater vigilance towards an area from which they had previously witnessed a threatening “stick attack” if a hidden causal agent (a human) could still be present in that area compared to when a human person had visibly left. Interpretations of these results were challenged in two commentaries (Boogert et al., 2013; Dymond et al., 2013). We aimed to replicate this experiment with a different group of NCCs (N = 14) whilst also adding three additional control groups that addressed the issues raised in the two commentaries. These four experimental groups included a direct replication (n = 4), a counter balance of the events of that replication (n = 4), a control group to see if alternative associative cues would create the same effect (n = 3) and finally, a counterbalanced group of these alternative associative cues (n = 3). The direct replication group did not replicate the effect of Taylor et al. (2012). The fact that we did not replicate the effect meant that further interpretation of our other control groups proved difficult. The low sample size of our replication group meant we could not be sure if we did not replicate the effect due to low power or due to actual differences. Our findings neither support nor refute whether NCCs reason about hidden causal agents.

Threat recognition and response in an avian brood-parasite host from New Caledonia

AbstractNest predation and avian brood parasitism are the main sources of nest failure in many passerine birds. Large predators threaten both brood and parents, whereas brood parasites pose only a danger to eggs or nestlings. The fan-tailed gerygone Gerygone flavolateralis from New Caledonia is subjected to high rates of nest predation by the New Caledonian crow Corvus moneduloides (responsible for about 20–40% of predation) and moderate rates of brood parasitism by the shining bronze-cuckoo Chalcites lucidus (parasitizing about 18% of nests), which also depredates nests that are too advanced for parasitism (13% of nests). To test if fan-tailed gerygones are able to discriminate predators from brood parasites, we presented 3 bird models at active gerygone nests: a brood parasite/small nest predator (shining bronze-cuckoo), a large nest predator (crow), and a small non-native bird (common chaffinch Fringilla coelebs), which is unknown to the gerygone, as a control. We assessed the response of adult gerygones to the presentation of each model by measuring the minimum approach distance, number of alarm calls, number of attacks, and time to first nest visit after the presentation (latency). Adult gerygones often attacked the cuckoo, approached but never attacked the chaffinch and always avoided the crow. Latency was shorter after an attack response and during brooding, but similar among models. We did not find any link between the cuckoo model presentation and later ejection of cuckoo nestlings. We conclude that adult fan-tailed gerygones discriminate between different models and respond accordingly to the level of threat, but do not show awareness of parasitism risk and increase of nestling ejection rates following exposure to the cuckoo model.

Decision-making flexibility in New Caledonian crows, young children and adult humans in a multi-dimensional tool-use task.

The ability to make profitable decisions in natural foraging contexts may be influenced by an additional requirement of tool-use, due to increased levels of relational complexity and additional work-effort imposed by tool-use, compared with simply choosing between an immediate and delayed food item. We examined the flexibility for making the most profitable decisions in a multi-dimensional tool-use task, involving different apparatuses, tools and rewards of varying quality, in 3-5-year-old children, adult humans and tool-making New Caledonian crows (Corvus moneduloides). We also compared our results to previous studies on habitually tool-making orangutans (Pongo abelii) and non-tool-making Goffin's cockatoos (Cacatua goffiniana). Adult humans, cockatoos and crows, but not children and orangutans, did not select a tool when it was not necessary, which was the more profitable choice in this situation. Adult humans, orangutans and cockatoos, but not crows and children, were able to refrain from selecting non-functional tools. By contrast, the birds, but not the primates tested, struggled to attend to multiple variables-where two apparatuses, two tools and two reward qualities were presented simultaneously-without extended experience. These findings indicate: (1) in a similar manner to humans and orangutans, New Caledonian crows and Goffin's cockatoos can flexibly make profitable decisions in some decision-making tool-use tasks, though the birds may struggle when tasks become more complex; (2) children and orangutans may have a bias to use tools in situations where adults and other tool-making species do not.

The crow in the room: New Caledonian crows offer insight into the necessary and sufficient conditions for cumulative cultural evolution.

New Caledonian (NC) crow populations have developed complex tools that show suggestive evidence of cumulative change. These tool designs, therefore, appear to be the product of cumulative technological culture (CTC). We suggest that tool-using NC crows offer highly useful data for current debates over the necessary and sufficient conditions for the emergence of CTC.

New Caledonian Crows Can Interconnect Behaviors Learned in Different Contexts, with Different Consequences, and After Exposure to Failure

Interconnection of behaviors is a process that describes how independently acquired behavioral repertoires can be combined together as a new sequence of behaviors. Manipulations of training, training context and experience of failure in the test situation can hinder this interconnection of previously acquired behaviors. We tested whether wild New Caledonian crows (Corvus moneduloides) could perform a sequence of six independently acquired behaviors in order to fetch a stone from inside a box in a nearby room and use it to gain food from a stone dropping apparatus. However, crows were only trained on three or four of the six behaviors required, and these prerequisites were trained in different contexts. One of the crows that learned four prerequisites solved the task. Neither of the crows that learned three prerequisites solved the task. The crows that learned four prerequisites, but did not solve the problem, were later trained in an additional behavior and then were able to solve the task. These results shows that New Caledonian crows are able to produce novel behavioral solutions to new problems by interconnecting behaviors learned in different contexts, with different consequences and despite experience of failure after the first exposure to the task.

Compound tool construction by New Caledonian crows

The construction of novel compound tools through assemblage of otherwise non-functional elements involves anticipation of the affordances of the tools to be built. Except for few observations in captive great apes, compound tool construction is unknown outside humans, and tool innovation appears late in human ontogeny. We report that habitually tool-using New Caledonian crows (Corvus moneduloides) can combine objects to construct novel compound tools. We presented 8 naïve crows with combinable elements too short to retrieve food targets. Four crows spontaneously combined elements to make functional tools, and did so conditionally on the position of food. One of them made 3- and 4-piece tools when required. In humans, individual innovation in compound tool construction is often claimed to be evolutionarily and mechanistically related to planning, complex task coordination, executive control, and even language. Our results are not accountable by direct reinforcement learning but corroborate that these crows possess highly flexible abilities that allow them to solve novel problems rapidly. The underlying cognitive processes however remain opaque for now. They probably include the species’ typical propensity to use tools, their ability to judge affordances that make some objects usable as tools, and an ability to innovate perhaps through virtual, cognitive simulations.

Determinants of data deficiency in the impacts of alien bird species

To identify the factors that influence the availability of data on the negative impacts of alien bird species, in order to understand why more than 70% are currently classified as Data Deficient (DD) by the Environmental Impact Classification of Alien Taxa (EICAT) protocol.Information on factors hypothesised to influence the availability of impact data were collated for 344 alien bird species (107 with impact data and 237 DD). These data were analysed using mixed effects models accounting for phylogenetic non‐independence of species (MCMCglmm).Data deficiency in the negative impacts of alien birds is not randomly distributed. Residence time, relative brain size and alien range size were found to be strongly related to the availability of data on impacts.The availability of data on the negative impacts of alien birds is mainly influenced by the spatial and temporal extents of their alien ranges. The results of this study suggest that the impacts of some DD alien birds are likely to be minor (e.g. species with comparatively long residence times as aliens, such as the common waxbill Estrilda astrild and the Java sparrow Padda oryzivora). However, the results also suggest that some DD alien birds may have damaging impacts (e.g. species from orders of alien birds known for their impacts to biodiversity but with comparatively small alien ranges, such as the New Caledonian crow Corvus moneduloides). This implies that at least some DD alien birds may have impacts that are being overlooked. Studies examining the traits that influence the severity of alien bird impacts are needed to help to predict which DD species are more likely to impact upon biodiversity.

From the Age of 5 Humans Decide Economically, Whereas Crows Exhibit Individual Preferences

Human societies greatly depend on tools, which spare us considerable time and effort. Humans might have evolved a bias to employ tools, using them even when they are unnecessary. This study aimed to investigate whether adult humans and a distantly related habitually tool-using vertebrate species, the New Caledonian crow (Corvus moneduloides), use tools depending on their necessity. In addition, children aged 3 to 5 years were examined to investigate the developmental pattern. The task involved choosing between using a body part (i.e. crows: beak; humans: hand) or a tool for retrieving a reward from a box. All subjects were tested in two conditions. In the Body+/Tool− condition, using the body was more efficient than using the tool, and conversely in the Body−/Tool+ condition. Our results suggest that the capacity to employ tools economically develops late in humans. Crows, however, failed to choose economically. At the individual level, some subjects exhibited striking individual preferences for either using a tool or their beak throughout the task. Whether such biases depend on individual experience or whether they are genetically determined remains to be investigated. Our findings provide new insights about tool use and its cognitive implementation in two outstanding tool-using taxa.

Function and flexibility of object exploration in kea and New Caledonian crows.

A range of non-human animals frequently manipulate and explore objects in their environment, which may enable them to learn about physical properties and potentially form more abstract concepts of properties such as weight and rigidity. Whether animals can apply the information learned during their exploration to solve novel problems, however, and whether they actually change their exploratory behaviour to seek functional information about objects have not been fully explored. We allowed kea (Nestor notabilis) and New Caledonian crows (Corvus moneduloides) to explore sets of novel objects both before and after encountering a task in which some of the objects could function as tools. Following this, subjects were given test trials in which they could choose among the objects they had explored to solve a tool-use task. Several individuals from both species performed above chance on these test trials, and only did so after exploring the objects, compared with a control experiment with no prior exploration phase. These results suggest that selection of functional tools may be guided by information acquired during exploration. Neither kea nor crows changed the duration or quality of their exploration after learning that the objects had a functional relevance, suggesting that birds do not adjust their behaviour to explicitly seek this information.

Safekeeping of tools in Goffin's cockatoos, Cacatua goffiniana

Tool use in animals can be costly as foraging tools need to be actively searched for or manufactured. Consequently, some habitually tool-using species keep their tools safe and ‘recycle’ them for further use. We tested the Indonesian Goffin's cockatoo, a parrot with the capacity but no apparent adaptive specialization for tool use to investigate how tool safekeeping can arise innovatively. In this case, we further intended to test whether and how such safekeeping changes in different feeding contexts. We demonstrate that, in a set-up allowing for tool losses, the birds quickly started to keep their tools safe in between tool-using events. They used different individual strategies, suggesting that the behaviour was a product of innovation rather than inherited predispositions. The frequency of safekeeping improved over time indicating individual learning. Furthermore, the birds flexibly adjusted their performance depending on different contexts: paralleling previous results in the habitually tool-using New Caledonian crow, Corvus moneduloides, the cockatoos saved their tools more often when the foraging site was elevated and when the food item was easy rather than difficult to process. Furthermore, when feeding at heights, the birds tended to use a different safekeeping mode than when the foraging site was low.

Invasive rats strengthen predation pressure on bird eggs in a South Pacific island rainforest.

Invasive rats (Rattus spp.) are known to have pervasive impacts on island birds, particularly on their nesting success. To conserve or restore bird populations, numerous invasive rat control or eradication projects are undertaken on islands worldwide. However, such projects represent a huge investment and the decision-making process requires proper assessment of rat impacts. Here, we assessed the influence of two sympatric invasive rats (Rattus rattus and R. exulans) on native bird eggs in a New Caledonian rainforest, using artificial bird-nest monitoring. A total of 178 artificial nests containing two eggs of three different sizes were placed either on the ground or 1.5 m high and monitored at the start of the birds’ breeding season. Overall, 12.4% of the nests were depredated during the first 7 days. At site 1, where nests were monitored during 16 days, 41.8% of the nests were depredated. The main predator was the native crow Corvus moneduloides, responsible for 62.9% of the overall predation events. Rats were responsible for only 22.9% of the events, and ate only small and medium eggs at both heights. Our experiment suggests that in New Caledonia, predation pressure by rats strengthens overall bird-nest predation, adding to that by native predators. Experimental rat control operations may allow reduced predation pressure on nests as well as the recording of biodiversity responses after rat population reduction.

‘Aesop's fable’ experiments demonstrate trial-and-error learning in birds, but no causal understanding

Experiments inspired by Aesop's fable The crow and the pitcher have been suggested to show that some birds (rooks, Corvus frugilegus, New Caledonian crows, Corvus moneduloides, and Eurasian jays, Garrulus glandarius) understand cause–effect relationships pertaining to water displacement. For example, the birds may prefer to drop stones in water rather than in sand in order to retrieve a floating food morsel, suggesting that they understand that only the level of water can be so raised. Here we re-evaluate the evidence for causal understanding in all published experiments (23 928 choices by 36 individuals). We first show that commonly employed statistical methods cannot disentangle the birds' initial performance on a task (which is taken as an indicator of causal understanding) from trial-and-error learning that may occur during the course of the experiment. We overcome this shortcoming with a new statistical analysis that quantifies initial performance and learning effects separately. We present robust evidence of trial-and-error learning in many tasks, and of an initial preference in a few. We also show that both seeming demonstrations of causal understanding and of lack of it can be understood based on established properties of instrumental learning. We conclude that Aesop's fable experiments have not yet produced evidence of causal understanding, and we suggest how the experimental designs can be modified to yield better tests of causal cognition.

Discovery of species-wide tool use in the Hawaiian crow.

Only a handful of bird species are known to use foraging tools in the wild. Amongst them, the New Caledonian crow (Corvus moneduloides) stands out with its sophisticated tool-making skills. Despite considerable speculation, the evolutionary origins of this species' remarkable tool behaviour remain largely unknown, not least because no naturally tool-using congeners have yet been identified that would enable informative comparisons. Here we show that another tropical corvid, the 'Alalā (C. hawaiiensis; Hawaiian crow), is a highly dexterous tool user. Although the 'Alalā became extinct in the wild in the early 2000s, and currently survives only in captivity, at least two lines of evidence suggest that tool use is part of the species' natural behavioural repertoire: juveniles develop functional tool use without training, or social input from adults; and proficient tool use is a species-wide capacity. 'Alalā and New Caledonian crows evolved in similar environments on remote tropical islands, yet are only distantly related, suggesting that their technical abilities arose convergently. This supports the idea that avian foraging tool use is facilitated by ecological conditions typical of islands, such as reduced competition for embedded prey and low predation risk. Our discovery creates exciting opportunities for comparative research on multiple tool-using and non-tool-using corvid species. Such work will in turn pave the way for replicated cross-taxonomic comparisons with the primate lineage, enabling valuable insights into the evolutionary origins of tool-using behaviour.

A novel tool-use mode in animals: New Caledonian crows insert tools to transport objects.

New Caledonian crows (Corvus moneduloides) rely heavily on a range of tools to extract prey. They manufacture novel tools, save tools for later use, and have morphological features that facilitate tool use. We report six observations, in two individuals, of a novel tool-use mode not previously reported in non-human animals. Insert-and-transport tool use involves inserting a stick into an object and then moving away, thereby transporting both object and tool. All transported objects were non-food objects. One subject used a stick to transport an object that was too large to be handled by beak, which suggests the tool facilitated object control. The function in the other cases is unclear but seems to be an expression of play or exploration. Further studies should investigate whether it is adaptive in the wild and to what extent crows can flexibly apply the behaviour in experimental settings when purposive transportation of objects is advantageous.Electronic supplementary materialThe online version of this article (doi:10.1007/s10071-016-1016-z) contains supplementary material, which is available to authorized users.

Social and Spatial Reintegration Success of New Caledonian Crows (Corvus moneduloides) Released after Aviary Confinement

ABSTRACT Wild birds are sometimes brought into captivity in order to conduct more controlled experiments, then released. Follow up work investigating how successful these birds are at reintegrating into their original habitats are rare. Here, I investigate the reintegration success of 13 New Caledonian Crows (Corvus moneduloides) who spent from 4–210 days in a large outdoor aviary in 2012 and 2014, then were released at their capture site. Five of the crows were monitored by telemetry for 2 weeks after their release in November 2014. In March and April 2015, 12 of the 13 crows were recorded at feeding sites where they were captured. The released crows showed a high degree of site fidelity and appeared to rapidly reintegrate with resident crows in the area. There were two cases of released crows successfully breeding. Long-term stay in captivity appears to have minimal impact on the ability of sub-adult and adult crows to re-establish their wild lifestyles, but juvenile crows <1 year old may find it more d...