Corvids Research Papers - Academia.edu (original) (raw)

- by Jeffrey Stevens
- •
- Animal Behavior, Animal Behaviour, Corvids, Prosocial Behavior

COOPERATIVE BREEDING IN CORVIDS (PASSERIFORMES, CORVIDAE)
O. A. Bresgunova
Сorvids with cooperative breeding form stable social units, where not only breeding pairs but helpers participate in feeding of young birds. In some other species, young birds stay with parents at their breeding areas,
but they do not demonstrate any helping behavior. Several factors (residence, stable environment, a lack of
favorable breeding areas, tolerance of adult birds, long social relations, social attachment, and fidelity to the
breeding territory of parent birds) may promote a delayed dispersal and helping behavior of the birds. The
prolonged family bonds founded on the tolerance of adult birds to juveniles and the long parental care were
shown to determine the delayed dispersal of young corvids. The appearance of accidental helpers at nests of
corvids with the delayed dispersal of young birds promotes the origin of traditional helping behavior in some
family lineages or populations.

- by Olga Bresgunova
- •
- Ornithology, Corvids, Birds, Corvidae

Human language involves combining items into meaningful, syntactically structured wholes. The evolutionary origin of syntactic abilities has been investigated by testing pattern perception capacities in nonhuman animals. New World primates can respond spontaneously to structural changes in acoustic sequences and songbirds can learn to discriminate between various patterns in operant tasks. However, there is no conclusive evidence that songbirds respond spontaneously to structural changes in patterns without reinforcement or training. In this study, we tested pattern perception capacities of common ravens, Corvus corax, in a habituationediscrimination playback experiment. To enhance stimulus salience, call recordings of male and female ravens were used as acoustic elements, combined to create artificial territorial displays as target patterns. We habituated captive territorial raven pairs to displays following a particular pattern and subsequently exposed them to several test and control playbacks. Subjects spent more time visually orienting towards the loudspeaker in the discrimination phase when they heard structurally novel call combinations, violating the pattern presented during habituation. This demonstrates that songbirds, much like primates, can be sensitive to structural changes in auditory patterns and respond to them spontaneously, without training.

- by Markus Böckle and +1
- •
- Psychology, Cognitive Psychology, Cognitive Science, Communication

Studies on members of the crow family using the “Aesop’s Fable” paradigm have revealed remarkable abilities in these birds, and suggested a mechanism by which associative learning and folk physics may interact when learning new problems. In the present study, children between 4 and 10 years of age were tested on the same tasks as the birds. Overall the performance of the children between 5-7-years was similar to that of the birds, while children from 8-years were able to succeed in all tasks from the first trial. However the pattern of performance across tasks suggested that different learning mechanisms might be being employed by children than by adult birds. Specifically, it is possible that in children, unlike corvids, performance is not affected by counter-intuitive mechanism cues.

- by Lucy Cheke
- •
- Developmental Psychology, Corvids, Causal Learning, Physical cognition

Crows are passerine birds of genus corvus in family Corvidae. Current study was carried out on three species of crow, jungle crow (Corvus macrorhynchos), house crow (C. splendens) and jackdaw (C. monedula) present in district Mansehra, Pakistan. Crows were trapped for blood sampling. The total genomic DNA was isolated from the blood of each species. The RAPD -PCR analysis of isolated DNA was performed for genetic diversity estimation. All the amplification profiles were observed and genetic distances were estimated. Results of RAPD analysis revealed high level of genetic polymorphism among the three species. The average genetic distance estimates ranged from 50-90%. Phylogenetic relationship was elaborated through dendrogram which supports the genetics distances. The dendrogram showed that house crow and jungle crow share much genetic affinities to each other than to jackdaw. The results also revealed the RAPD markers as effective for such types of studies where an overall picture of genome is required.

- by Sawar Khan
- •
- Botany, Zoology, Developmental Psychology, Environmental Education

I have long viewed ravens positively, thinking of them sometimes as a sort of quiet, usually distantly perched or invisible from me guardian angels of my woodland garden on Whidbey Island. For years I used to pester my then college-age older son about how they are not really normal birds in our surrounding woods. So now having read part of one of the excellent scientific studies by Marzluff and Angell (Gifts of the Crow), I decided to start writing down some of my experiences more systematically.

- by David Jackson
- •
- Corvids, Corvidae, Ravens, The Raven

Expertos en derecho ambiental y conservación de especies amenazadas analizan en el siguiente artículo las más de cien sentencias penales dictadas en España a los envenenadores de fauna salvaje. Sus conclusiones y recomendaciones deberían... more

- by Zebensui Morales-Reyes and +2
- •
- Zoology, Conservation Biology, Raptors, Corvids

Recent research with Rooks has demonstrated
impressive tool-using abilities in captivity despite this
species’ classification as a non-tool-user in the wild. Here,
we explored whether another non-tool-using corvid, the
Eurasian Jay, would be capable of similar feats and
investigated the relative contributions of causal knowledge
and instrumental conditioning to the birds’ performance on
the tasks. Five jays were tested on a variety of tasks
involving water displacement. Two birds reliably interacted
with the apparatuses. In these tasks, both birds
showed a preference for inserting stones into a tube containing
liquid over a tube containing a solid or a baited
‘empty’ tube and also for inserting sinkable items over
non-sinkable items into a tube of water. To investigate the
contribution of instrumental conditioning, subjects were
then tested on a series of tasks in which different cues were
made available. It was found that, in the absence of any
apparent causal cues, these birds showed a clear preference
for the rewarded tube when the food incrementally
approached with every stone insertion, but not when it
simply ‘‘appeared’’ after the correct number of stone
insertions. However, it was found that subjects did not
prefer to insert stones into a tube rewarded by the incremental
approach of food if the available causal cues
violated the expectations created by existing causal
knowledge (i.e. were counter-intuitive). An analysis of the
proportion of correct and incorrect stone insertions made in
each trial across tasks offering different types of information
revealed that subjects were substantially more successful
in experiments in which causal cues were available,
but that rate of learning was comparable in all experiments.
We suggest that these results indicate that Eurasian jays use
the incremental approach of the food reward as a conditioned
reinforcer allowing them to solve tasks involving
raising the water level and that this learning is facilitated
by the presence of causal cues.

- by Lucy Cheke
- •
- Associative Learning and Memory, Animal Cognition, Causality, Tool-Use

Intentional poisoning is a global wildlife problem and an overlooked risk factor for public health. Managing poisoning requires unbiased and high-quality data through wildlife monitoring protocols, which are largely lacking. We herein evaluated the biases associated with current monitoring programmes of wildlife poisoning in Spain. We compared the national poisoning database for the 1990–2015 period with information obtained from a field experiment during which we used camera-traps to detect the species that consumed non-poisoned baits. Our findings suggest that the detection rate of poisoned animals is species-dependent: Several animal groups (e.g., domestic mammalian carnivores and vultures) tended to be over-represented in the poisoning national database, while others (e.g., corvids and small mammals) were underrepresented. As revealed by the GLMM analyses, the probability of a given species being overrepresented was higher for heaviest, aerial, and cryptic species. In conclusion...

Animals are predicted to selectively observe and learn from the conspecifics with whom they share social connections. Yet, hardly anything is known about the role of different connections in observation and learning. To address the relationships between social connections, observation and learning, we investigated transmission of information in two raven (Corvus corax) groups. First, we quantified social connections in each group by constructing networks on affiliative interactions, aggressive interactions and proximity. We then seeded novel information by training one group member on a novel task and allowing others to observe. In each group, an observation network based on who observed whose task-solving behaviour was strongly correlated with networks based on affiliative interactions and proximity. Ravens with high social centrality (strength, eigenvector, information centrality) in the affiliative interaction network were also central in the observation network, possibly as a result of solving the task sooner. Network-based diffusion analysis revealed that the order that ravens first solved the task was best predicted by connections in the affiliative interaction network in a group of subadult ravens, and by social rank and kinship (which influenced affiliative interactions) in a group of juvenile ravens. Our results demonstrate that not all social connections are equally effective at predicting the patterns of selective

- by Ipek G Kulahci and +1
- •
- Social Network Analysis (SNA), Social learning, Corvids

O.A. Bresgunova. Magpie (Pica pica) roosts: individual behavioural strategies,
communal roosts’ organization and habitat preference. – The organization of communal roost
is poorly understood in most corvids. I investigated the distribution of main communal roosts
and sub-roosts of Magpie (Pica pica). 15 cluster Magpie roosts, which include main
roost sites and several sub-roosts, were discovered in Kharkov city in 2002-2009 years. The
general numbers of Magpies’ population within Kharkov city vary in different years from 6500
to 8000 ind. (mean 7360 ind.; n = 5). The Magpie is a sedentary species and maintains breeding
territories year-round while travelling long distances (from 1,7 to 6,5 km, mean 3,95 km; n = 15)
to roost communally at night in wintertime. The catchment area of communal roosts varied
from 3,6 to 50 km² (n = 15). All Magpie communal roosts include main roost with 1‑3 sites
for sleeping (which Magpies use simultaneously or in different years) and some sub-roosts.
The main roosts exist year-round on traditional territories. The Magpies form sub-roosts from
April to November and after sub-roost departure birds congregate on main roost sites. The
distance between main communal roost site and sub-roosts sites vary from 1,8 to 4,7 km (mean
3,6 km; n = 5). 80,55% of main communal roost sites are confined to floodplain terraces and
birds prefer to sleep in willow (Salix cinerea) bushes and reeds (Phragmites australis) (61,11%)
(n = 36). The more are the numbers of Magpies on communal roost site in winter the more is
the catchment area of the roost (Spearman rank correlation R = 0,956; p < 0,01), the more is
the maximum catchment radius of the roost (R = 0,716; p < 0,01), and the more individuals
participate in roost formation in breeding period (R = 0,803; p < 0,01). The numbers of Magpies
at main roost sites don’t change from early December to the end of February. The numbers of
roosting Magpies decline from the end of March – early April. Minimum numbers of Magpies
was observed at main roost sites in April and May. In breeding period main roosts were mainly
joined by non-breeding Magpies, first-year birds and breeders from breeding territories, which
are closer 500 m to main roost sites. From August the numbers of roosting Magpies start toincrease. Main roosts include more communal roosting birds in breeding period than sub-roosts
(Mann‑Whitney U test; U = 17, p < 0,01). Consequently, non-breeding birds prefer to roost at
main roost sites. The breeding Magpies have two types of roosting behaviour in breeding period.
Females usually don’t join communal roost and often roost at the nest until fledglings leave
it. If the breeding territory is situated near communal roost site (up to 500 m) and fledglings
already left the nest females may fly to communal roost in the night. If the breeding territory
is nearby communal roost site (up to 500 m) breeding males travel to roost communally at
night when females incubate and brood and when fledglings already left the nest. Two adult
Magpies roosted on breeding territory in incubation and brooding periods but the distance
between their breeding sites and communal roost site exceeds 700 m. When the fledglings left
the nests on these territories, only one parent bird remains on breeding territory, another adult
bird participates in communal roost gathering. Distance between breeding territory and communal
roost, stage of breeding cycle and roosting behaviour of adjacent breeding pairs play
key roles in Magpie roosting strategies in breeding period. The Magpie’ broods roost within
parent breeding territory for 20‑40 days after leaving the nest. At age of 50‑65 days young birds
start to participate in communal roost gathering. The Magpies form pre-roosting
gatherings at breeding territories, near sites of traditional sub-roosts and along the way to roost
sites on tree tops (conifers and deciduous trees), in bushes and on roofs of buildings.

- by Olga Bresgunova
- •
- Ornithology, Corvids, Corvidae, Birds Ecology and Behaviour

O.A. Bresgunova. Notes on Jay (Garrulus glandarius) roosts in Kharkov
city. — Roosting and pre-roosting behaviour of Jays (Garrulus glandarius) was investigated
in Kharkov city in 2010 – 2012. The size of pre-roosting aggregations of Jays is 4 to 15 birds.
Our study showed that Jays prefer to use Norway spruce (Picea abies) trees for roosting
(171 observations) in the course of a year. The birds rest on spruce branches at 4 – 13 m
above the ground (12,8% — at 4 – 6 m, 55,3% — at 7-9 m, 31,9% — at 10 – 13 m; n = 94).
In October (rarely August) to March the Jays also use for roosting Lombardy poplar (Populus
italica) trees. The birds settle on lateral branches near the trunk. We discovered 20 roosting
places of Jays on Lombardy poplar trees (30 observations). On poplar branches Jays roost
at 4,5 to 12 m above the ground (average 6,6 m; n = 20). Also Jays rarely roost on Norway
maple (Acer platanoides) (June-August), Sugar maple (A. saccharum) (June – August),
White poplar (Pоpulus аlba) (August), Grey willow (Salix cinerea) (winter), and Hawthorn
(Crataegus sp.) (winter). Jays settle for roosting at varying times e.g. as early as 2 hour
40 minutes before sunset to as late as 20 minutes after sunset. In July to March Jays settle
for roosting on average 45,4 minutes before sunset (n = 34). Some birds go to sleep with
difference of 30 – 40 minutes in the same evening (2 observations; February). Jays showed
morning activity 15 – 30 minutes before sunrise (3 observations; November, February, March).

- by Olga Bresgunova
- •
- Ornithology, Corvids, Birds, Corvidae

Corvids are often viewed as efficient predators capable of limiting prey species populations.
Despite this widely held belief, a comprehensive review quantifying the effect of
corvids on the demography of prey species is lacking. We examine the impacts of crows,
ravens Corvus spp. and Eurasian Magpies Pica pica on the population parameters of
other bird species. We summarize results from 42 studies, which included 326 explicit
evaluations of relationships between a corvid and a potential prey species. Population
parameters of studied prey species were categorized as abundance-related (numbers, nest
density) or productivity-related (nest success, brood size). Information from both experimental
removal studies and correlative studies was examined. Combining all studies, no
negative influence of corvids on either abundance or productivity of prey species was
found in 81% of cases. Negative impacts were significantly more likely in cases examining
productivity rather than abundance (46 vs. 10%). Experimental studies that removed
only corvid species were significantly less likely to show a positive impact on productivity
than those removing corvids alongside other predators (16 vs. 60%). This suggests that
the impact of corvids is smaller than that of other predators, or that compensatory predation
occurs. The impact of corvids was similar between diverse avian groups (such as
gamebirds, passerines and waders; or ground-nesting and other species). Crows were
found to be significantly more likely to have a negative impact on prey species productivity
than were Magpies (62 vs. 12%), but no differences were found in relation to prey
abundance. We conclude that while corvids can have a negative impact on bird species,
their impact is small overall, and nearly five times more frequent for productivity than
for abundance. These results suggest that in most cases bird populations are unlikely to
be limited by corvid predation and that conservation measures may generally be better
targeted at other limiting factors. However, negative impacts were found in a minority
of cases, and those may require further investigation to develop management tools to
mitigate such impacts where they are of economic or conservation concern.

- by Arjun Amar
- •
- Conservation Biology, Conservation, Ecology, Animal Ecology

Aim Climate change and other anthropogenic global change drivers act in complex, mutually exacerbating ways to alter the abundance and distribution of species. In South Africa, pied crows Corvus albus have increased in numbers and range in recent decades. Popular opinion links these changes to urbanisa-tion and infrastructure development, but there has been no empirical test of this idea. We aimed to clarify the drivers of pied crow population changes in South Africa.

- by Arjun Amar and +1
- •
- Ornithology, Climate Change, Renewable Energy, Energy

Multi-species communal roosts with participation of Magpie. Bresgunova O.A. – I recorded roosting behaviour of the Magpie (Pica pica) in 15 roost sites in 2003/2004, 2004/2005 and 2005/2006 winters. My goal was to discover avian species, which form multi-species roosts with Magpie at the same locations. The Fieldfare (Turdus pilaris), Starling (Sturnus vulgaris), Hooded Crows (Corvus cornix), Rooks (C. frugilegus), Jackdaws (C. monedula), Water Rail (Rallus aquaticus), Redwings (Turdus merula), Song Thrushes (T. philomelos), Blue Tits (Parus caeruleus), Great Tits (P. major), European Greenfinches (Chloris chloris), Eurasian Siskins (Spinus spinus), Eurasian Linnets (Acanthis cannabina), Tree Sparrows (Passer montanus) and Waxwings (Bombycilla garrulus) form mixed communal roosts on the traditional Magpie roost sites.

- by Olga Bresgunova
- •
- Ornithology, Corvids, Corvidae, Roosting behaviour

En la primavera del 2009 comenzó en América del Norte la pandemia de gripe por el virus H1N1, que se propagó rápi damente por el mundo y suscitó un gran interés en las posibles estrategias de miti gación para hacer frente a la primera pandemia de gripe en más de 40 años. Las investigaciones se centraron en RESUMEN Evaluamos el uso en la salud pública del número reproductivo básico (R 0), por el cual se estima la velocidad con que una enfermedad puede propagarse en una población. Estas estimaciones son de gran interés en el campo de la salud pública como quedó de manifiesto en ocasión de la pandemia del 2009 por el virus gripal A (H1N1). Revisamos los métodos usados comúnmente para estimar el R 0 , examinamos su utilidad práctica y determinamos la forma en que las estimaciones de este parámetro epidemiológico pueden servir de fundamento para tomar decisiones relativas a las estrategias de mitigación. Por sí solo, el R 0 es una medida insuficiente de la dinámica de las enfermedades infecciosas en las poblaciones; hay otros parámetros que pueden aportar información más útil. No obstante, la estimación del R 0 en una población determinada es útil para entender la transmisión de una enfermedad en ella. Si se considera el R 0 en el contexto de otros parámetros epidemiológicos importantes, su utilidad puede consistir en que permite conocer mejor un brote epidémico y preparar la respuesta de salud pública correspondiente. Pan American Journal of Public Health inter venciones, como el distanciamiento social, que pudieran aplicarse antes de que se obtuviera una vacuna monovalente específica contra el virus H1N1, lo que ocurrió en el otoño del 2009. En plena oleada inicial de la pandemia, grupos de especialistas en modelización de todo el mundo comenzaron a reunir datos proce dentes de México para determinar varias características del virus nuevo (1, 2). Las actividades se concentraron en la estima ción rápida del número reproductivo bási co (R 0) del virus. El R 0 es un parámetro teórico que proporciona cierta informa ción acerca de la velocidad con que una enfermedad puede propagarse en una po blación determinada. Las primeras estima ciones se publicaron en línea a principios de mayo del 2009 (1, 2). Se siguen publi cando estimaciones del R 0 de otros países y a medida que hay más datos (3-11). Como indicio del interés suscitado por las publicaciones acerca del R 0 , el artículo de Fraser et al., una publicación tempra na sobre el potencial pandémico del vi rus H1N1 2009, se había citado 654 veces al 7 de febrero del 2013. La pandemia de gripe explica una buena parte del interés reciente en el número reproductivo bási co, pero dicho interés no se circunscribe al campo de la gripe. La búsqueda de los términos "reproduction number" o "re productive number" en la Web of Scien ce indicó que entre el 2009 y el 7 de fe brero del 2013 se habían publicado 710 artículos sobre este tema en diversas SECCIÓN ESPECIAL / SPECIAL SECTION *Traducción oficial al español del artículo original en inglés efectuada por la Organización Pana mericana de la Salud, con autorización de la American Public Health Association. En caso de discrepancia entre ambas versiones, prevalecerá la original (en inglés). © Organización Panamericana de la Salud, 2015, ver sión en español. Todos los derechos reservados.

- by Alejandro Stern
- •
- Corvids, Corvidae

In recent decades, intensive techniques of livestock raising have flourished, which has largely replaced traditional farming practices such as transhumance. These changes may have affected scavengers' behaviour and ecology, as extensive livestock is a key source of carrion. This study evaluates the spatial responses of avian scavengers to the seasonal movements of transhumant herds in southeastern Spain. We surveyed the abundance of avian scavengers and ungulates, and analysed the factors affecting the space use by 30 GPS-tracked griffon vultures (Gyps fulvus). Griffons' foraging activity increased in the pasturelands occupied by transhumant herds, which implied greater vulture abundance at the landscape level during the livestock season. In contrast, facultative scavengers were more abundant without transhumant livestock herds, and the abundance of wild ungulates did not change in relation to livestock presence. We conclude that fostering transhumance and other traditional farming systems, to the detriment of farming intensification, could favour vulture conservation.

- by Zebensui Morales-Reyes
- •
- Ecology, Corvids, Biodiversity Conservation, Ungulates

Food sharing offers a clear example of prosocial behaviour, in which one individual's actions benefit another. Researchers have proposed a range of hypotheses that explain why food sharing may occur among unrelated individuals. Two such hypotheses, reciprocity and dominance, have been tested in many species, including fish, corvids, rats, bats and primates, showing that (1) recipients sometimes reciprocate sharing back to previous donors and (2) dominant individuals share more than subordinates. Although primates dominate the study of prosocial behaviour, active donation of food is actually quite rare in primates. In contrast, several corvid species spontaneously share food much more frequently. Here, we explored the role of reciprocity and dominance in spontaneous food sharing among male pinyon jays, Gymnorhinus cyanocephalus, a North American corvid species that exhibits high levels of social complexity. Unlike much of the previous work, we tested prosocial behaviour among unrelated, non-pair-bonded adults. We observed high levels of active sharing, and donors showed clear preferences with whom they shared. We found no evidence that pinyon jays reciprocated shares in either the short or long term. This was true for both sharing within dyads (direct reciprocity) and sharing irrespective of most recent partner identity (generalized reciprocity). However, dominance influenced sharing in one of our squads, with dominant individuals sharing more than subordinates. This study highlights corvids as a fruitful model for the study of the proximate mechanisms underlying naturally occurring prosocial behaviours.

- by Juan F Duque
- •
- Animal Behavior, Corvids, Prosocial Behavior, Food sharing

Choice by exclusion involves selecting a rewarded stimulus by rejecting alternatives that are unlikely to be rewarded. It has been proposed that in corvids, exclusion is an adaptive specialization for caching that, together with object permanence and observational spatial memory, enhances a bird’s ability to keep track of the contents of caches. Thus, caching species are predicted to perform well in tasks requiring exclusion. We tested this prediction by assessing the performance of Eurasian jays (Garrulus glandarius), a highly specialized cacher, in a two-way object choice task in which food was hidden in 1 of 2 cups. Consistent with the corvids’ capacity for observational spatial memory, jays were highly accurate when shown the location of the food reward. However, the jays failed to exclude the empty cup when shown its contents. This failure to select the baited cup when shown the empty cup was possibly due to jays attending to the experimenter’s movements and erroneously selecting the empty cup by responding to these local enhancement cues. To date, no corvids have been tested in an auditory two-way object choice task. Testing exclusion in the auditory domain requires that a bird use the noise produced when the baited cup is shaken to locate the reward. Although jays chose the baited cup more frequently than predicted by chance, their performance did not differ from trials controlling for the use of conflicting cues provided by the experimenter. Overall, our results provide little support for the hypothesis that caching has shaped exclusion abilities in corvids.

- by Rachael C Shaw
- •
- Corvids

Corvids such as jays and ravens cache food for future consumption and can remember the location of caches that they have seen others make. Given the risk of caches being pilfered by observers, corvids limit opportunities for conspecifics to witness caching events. Faced with cache protection tactics, pilferers should also utilize tactics to maximize their success. Cacher–pilferer interactions and their underlying cognition have largely been investigated in semisocial ravens, Corvus corax, and western scrub-jays, Aphelocoma californica. However to understand the factors influencing the development of these abilities, data are required from species that differ in their socioecology from ravens and western scrub-jays. In the current study, we tested the caching and pilfering behaviour of territorial Eurasian jays in two social contexts. In one context, subjects competed with a dominant conspecific, while in the other the same individuals interacted with a subordinate competitor. When subordinate, birds initially suppressed caching, before caching more in less exposed locations. In contrast, when socially dominant, birds cached more and moved items multiple times. As subordinate pilferers, birds took longer to approach cache sites and approached when the cacher was at a distance, while when dominant, birds rapidly approached the conspecifics’ cache sites, frequently when the cacher was still in the process of caching. Individual jays therefore flexibly switched caching and pilfering tactics in response to the relative dominance of their competitor. We discuss the implications of our results for competing theories on the origin of behavioural flexibility and its underlying complex cognition in the corvid lineage.

- by Rachael C Shaw
- •
- Social Cognition, Corvids
- by Jennifer Vonk
- •
- Corvids, Relational Reasoning

Food caching animals depend on their caches at times of low food availability. Because stored food is susceptible to being stolen or degraded, many species employ cache protection strategies such as ceasing caching in the presence of others or avoiding storing perishable items for long periods. Several species frequently recover their caches and recache, which may reduce pilferage or degradation of cached items. We studied the food handling decisions of Florida scrub-jays (Aphelocoma coerulescens) after cache recovery to determine the roles that social and ecological environments play in post-recovery decisions. Instead of reducing recaching in the presence of others, recovering jays flew away from the recovery site, allowing them to eat or recache a recovered item regardless of the social context. Microhabitat type and soil moisture of the recovery sites had a significant influence on whether recoveries were eaten or recached; most items that were recached had been recovered from bare sand sites or sites with low soil moisture. Taken together, our results suggest that food store management of Florida scrub-jays are unaffected by the social context, but are strongly affected by the habitat conditions that influence the quality of caches.

- by Ipek G Kulahci
- •
- Animal Behavior, Animal Cognition, Corvids

Self-control underlies cognitive abilities such as decision making and future planning. Delay of gratification is a measure of self-control and involves obtaining a more valuable outcome in the future by tolerating a delay or investing a greater effort in the present. Contextual issues, such as reward visibility and type, may influence delayed gratification performance, although there has been limited comparative investigation between humans and other animals, particularly non-primate species. Here, we adapted an automated 'rotating tray' paradigm used previously with capuchin monkeys to test for delay of gratification ability that requires little pre-test training, where the subject must forgo an immediate, less preferred reward for a delayed, more preferred one. We tested New Caledonian crows and 3-5-year-old human children. We manipulated reward types to differ in quality or quantity (Experiments 1 and 2) as well as visibility (Experiment 2). In Experiments 1 and 2, both species performed better when the rewards varied in quality as opposed to quantity, though performed above chance in both conditions. In Experiment 1, both crows and children were able to delay gratification when both rewards were visible. In Experiment 2, 5-year-old children outperformed 3-and 4-year olds, though overall children still performed well, while the crows struggled when reward visibility was manipulated, a result which may relate to difficulties in tracking the experiment-ers' hands during baiting. We discuss these findings in relation to the role of contextual issues on self-control when making species comparisons and investigating the mechanisms of self-control.

- by Rachael Miller (Harrison) and +1
- •
- Cognition, Child Development, Corvids
- by Olga Bresgunova
- •
- Ornithology, Corvids, Corvidae, Roosting behaviour
- by Ivan Sebalo
- •
- Ethology, Biology, Corvids, Crows

Knowledge about the causal relationship between objects has been studied extensively in human infants, and more recently in adult animals using differential looking time experiments. How knowledge about object support develops in non-human animals has yet to be explored. Here, we studied the ontogeny of support relations in Eurasian jays (Garrulus glandarius), a bird species known for its sophisticated cognitive abilities. Using an expectancy violation paradigm, we measured looking time responses to possible and impossible video and image stimuli. We also controlled for experience with different support types to determine whether the emergence of support intuitions is dependent upon specific interactions with objects, or if reasoning develops independently. At age 9 months, birds looked more at a tool moving a piece of cheese that was not in contact than one that was in direct contact. By the age of 6 months, birds that had not experienced string as a support to hold up objects looked more at impossible images with string hanging from below (unsupported), rather than above (supported). The development of support intuitions may be independent of direct experience with specific support, or knowledge gained from interactions with other objects may be generalised across contexts. The ability to reason about objects and how they relate to one another is an important part of interacting with the physical world. By knowing that an object will fall if not supported from below, one can ensure the correct placement of objects on stable surfaces. Intuitions about support may be dependent on developing rules about observable support (e.g. other objects) and unobservable phenomena (e.g. gravity). Objects can interact in several different ways, and studies with human infants indicate that they develop intuitions about different categories of support at different ages 1–4. At the age of 3 months, infants understand the basic concept that objects must be in contact in order to be supported. By 4.5 months of age, they recognise that the positioning of contact is also important (i.e. an object needs to be underneath another object, rather than in contact along the vertical edges) 2. At 6.5 months of age, they distinguish between the amount of contact that is necessary for one object to be supported by another. Objects can also interact when colliding with one another. In 'launching events' , objects can be shown to move relative to each other in possible and impossible ways. It is not until 6–7 months of age that infants are sensitive to no contact collision events (i.e. the second object moves before an approaching object makes physical contact with it) compared to contact collision events (i.e. the second object moves only once the first object collides with it) 5,6. Comparative studies on adult animals has shown that chimpanzees (Pan troglodytes) 7,8 and monkeys (Macaca fuscata) 8 distinguish between contact vs no contact and amount of contact, but do not distinguish between the position (i.e. type) of contact. These studies suggest that apes and monkeys differ from infants in their understanding of the support 7. A phylogenetically distant species, the rook (Corvus frugilegus) has also been tested using a similar paradigm, and perceived these three categories of support in the same way as 6.5 month old infants 9. There is growing evidence that corvids (e.g. crows, rooks and jays) have sophisticated levels of causal reasoning in the physical domain (i.e. the understanding of how and why cause and effect relationships work), e.g. refs 10–13. New Caledonian crows not only use tools to gain access to grubs in tree crevices in the wild 14 ,

- by Rachael Miller (Harrison) and +2
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- Causal reasoning, Corvids

Corvids (birds in the crow family) are hypothesised to have a general cognitive tool-kit because they show a wide range of transferrable skills across social, physical and temporal tasks, despite differences in socioecology. However, it is unknown whether relatively asocial corvids differ from social corvids in their use of social information in the context of copying the choices of others, because only one such test has been conducted in a relatively asocial corvid. We investigated whether relatively asocial Eurasian jays (Garrulus glandarius) use social information (i.e., information made available by others). Previous studies have indicated that jays attend to social context in their caching and mate provisioning behaviour; however, it is unknown whether jays copy the choices of others. We tested the jays in two different tasks varying in difficulty, where social corvid species have demonstrated social information use in both tasks. Firstly, an object-dropping task was conducted requiring objects to be dropped down a tube to release a food reward from a collapsible platform, which corvids can learn through explicit training. Only one rook and one New Caledonian crow have learned the task using social information from a demonstrator. Secondly, we tested the birds on a simple colour discrimination task, which should be easy to solve, because it has been shown that corvids can make colour discriminations. Using the same colour discrimination task in a previous study, all common ravens and carrion crows copied the demonstrator. After observing a conspecific demonstrator, none of the jays solved the object-dropping task, though all jays were subsequently able to learn to solve the task in a non-social situation through explicit training, and jays chose the demonstrated colour at chance levels. Our results suggest that social and relatively asocial corvids differ in social information use, indicating that relatively asocial species may have secondarily lost this ability due to lack of selection pressure from an asocial environment.

- by Rachael Miller (Harrison)
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- Social learning, Corvids

O.A. Bresgunova. - Companions of the magpie at communal roosts.
I observed roosting behaviour of the Magpie (Pica pica) in 15 communal winter roost congregations
that used a total of 28 sites for roosting in Kharkov in 2003–2009, three in the Kharkov Region in 2005–2009 and one in Kiev in 2007. My goal was to find out which species form multi-species roosts with the Magpie at the same locations. In Kharkov, Magpie roost congregations exist all year round. WeWe found 15 communal roosts of the Fieldfare (Turdus pilaris) and the Magpie in Kharkov and three in Kharkov Region. Magpies outnumber the Fieldfares at the majority of communal roosts. The maximal numbers of the Magpie in the mixed congregations was about 2 500 and the numbers of the Fieldfare in them was 600. The Starling (Sturnus vulgaris) share communal night roost with the Magpie from April to December with the maximal numbers of 650 in August through October. In addition, Starlings form huge (about 3 000 individuals) winter roost congregations on the Magpies’ roost sites. Hooded Crows (Corvus cornix), Rooks (C. frugilegus), and Jackdaws (C. monedula) also form roost congregations on one of the magpie roost sites in Kharkov and on one in Kiev. In Kharkov, the numbers of roosting Magpies vary from 30 to 150 depending on the period of year. Hooded Crows form communal roost from mid-October to early April in the same location. Magpies arrived at the roost site independently and earlier than Crows and formed compact roosting group. The Crows’ arrival forced Magpies to change roosting place and spend the night in several other places. Eurasian Tree Sparrows (Passer montanus) share roosts with the Magpie on seven traditional communal roost sites. WeWe recorded Blackbirds (Turdus merula), Song Thrushes (T. philomelos), Redwing (T. iliacus), European Robin (Erithacus rubecula), Common Ravens (Corvus corax), Eurasian Jays (Garrulus glandarius), Blue Tits (Parus caeruleus), Great Tits (P. major), European Greenfinches (Chloris chloris), Eurasian Siskins (Spinus spinus), Eurasian Linnets (Acanthis cannabina), European Goldfinches (Carduelis carduelis), Hawfinches
(Coccothraustes coccothraustes), Chaffinches (Fringilla coelebs), Eurasian Bullfinches (Pyrrhula pyrrhula),
Yellowhammers (Emberiza citrinella), White WaWagtails (Motacilla alba), Citrine WaWagtail (Motacilla citreola), Northern House-Martins (Delichon urbica), Barn Swallows (Hirundo rustica), Sand Martins (Riparia
riparia), WaWaxwings (Bombycilla garrulus), and WaWater Rail (Rallus aquaticus) on the traditional Magpies’ communal roost sites. Thus, 29 companion species were found on the traditional communal roost sites of the Magpies.

- by Olga Bresgunova
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- Ornithology, Corvids, Corvidae, Roosting behaviour

Vegetation dynamics in complex landscapes depend on interactions among environmental heterogeneity, disturbance, habitat fragmentation, and seed dispersal processes. We explore how these features combine to affect the regional abundances and distributions of three Quercus (oak) species in central Spain: Q. faginea (deciduous tree), Q. ilex (evergreen tree), and Q. coccifera (evergreen shrub). We develop and parameterize a stochastic patch occupancy model (SPOM) that, unlike previous SPOMs, includes environmentally driven variation in disturbance and establishment. Dispersal in the model is directed toward local (nearby) suitable habitat patches, following the observed seed-caching behavior of the European Jay. Model parameters were estimated using Bayesian methods and survey data from 12 047 plots. Model simulations were conducted to explore the importance of different dispersal modes (local directed, global directed, local random, global random). The SPOM with local directed dispersal gave a much better fit to the data and reproduced observed regional abundance, abundance-environment correlations, and spatial autocorrelation in abundance for all three species. Model simulations suggest that jay-mediated directed dispersal increases regional abundance and alters species-environment correlations. Local dispersal is estimated to reduce regional abundances, amplify species-environment correlations, and amplify spatial autocorrelation. Parameter estimates and model simulations reveal important species-specific differences in sensitivity to environmental perturbations and dispersal mode. The dominant species Q. ilex is estimated to be highly fecund, but on the edge of its climatic tolerance. Therefore Q. ilex gains little from directed dispersal, suffers little from local dispersal, and is relatively insensitive to changes in habitat cover or disturbance rate; but Q. ilex is highly sensitive to altered drought length. In contrast, the rarest species, Q. coccifera, is well adapted to the climate and soils but has low fecundity; thus, it is highly sensitive to changes in dispersal, habitat cover, and disturbance but insensitive to altered drought length. Finally, Q. faginea is estimated to be both at the edge of its climatic tolerance and to have low fecundity, making it sensitive to all perturbations. Apparently, co-occurring species can exhibit very different interactions among dispersal, environmental characteristics, and physiological tolerances, calling for increased attention to species-specific dynamics in determining regional vegetation responses to anthropogenic perturbations.

- by Fernando Prieto
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- Environmental Science, Climate Change, Migration, Ecology

Humans and other animals often favour immediate gratification over long-term gain. Primates, including humans, appear more willing to wait for rewards than other animals, such as rats or pigeons. Another group displaying impressive patience are the corvids, which possess large brains and show sophisticated cognitive abilities. Here, we assess intertemporal choice in one corvid species, the Western scrub-jay (Aphelocoma californica). These birds cache food for future consumption and respond flexibly to future needs. Cache-theft and cache-degradation are time-dependent processes in scrub-jay ecology that might necessitate sensitivity to delays between caching and retrieval. We adopt a caching paradigm with delays of up to 49 h. Across two experiments we find no evidence of a preference for earlier recovery. We highlight the possibility that, although scrub-jays can discriminate between the present and the future, they may not understand how far into the future an event will occur.

- by Nicky S Clayton
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- Psychology, Cognitive Science, Comparative Cognition, Diet

There is growing comparative evidence that the cognitive bases of cooperation are not unique to humans. However, the selective pressures that lead to the evolution of these mechanisms remain unclear. Here we show that while tool-making New Caledonian crows can produce collaborative behavior, they do not understand the causality of cooperation nor show sensitivity to inequity. Instead, the collaborative behavior produced appears to have been underpinned by the transfer of prior experience. These results suggest that a number of possible selective pressures, including tool manufacture and mobbing behaviours, have not led to the evolution of cooperative cognition in this species. They show that causal cognition can evolve in a domain specific manner-understanding the properties and flexible uses of physical tools does not necessarily enable animals to grasp that a conspecific can be used as a social tool.

- by Russell Gray
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- Animal Behavior, Cognition, Animal Cognition, Multidisciplinary

It is well-known that some members of the crow family (Corvidae) are important for seed dispersal either via frugivory (e.g., when feeding on berries) or by scatter hoarding (e.g., of nuts). Dispersal via gut passage of seeds within a fleshy fruit can be considered "classical endozoochory." However, corvids are rarely recognized as vectors of plants lacking a fleshy fruit, or a large nut (such as plants with a dry achene, capsule or caryopsis). Dispersal of such seeds via gut passage can be considered "non-classical endozoochory." A century ago, Heintze (1917a,b); Heintze (1918) reported on extensive field studies of seed dispersal by 11 species of European Corvidae. His work is overlooked in contemporary reviews of corvid biology. We resurrect his work, which suggests that contemporary views about seed dispersal by corvids are too narrow. Heintze identified 157 plant taxa from 42 families which were dispersed by corvids by endozoochory, as well as another nine taxa only dispersed by synzoochory (which includes scatter-hoarding). Most (54%) of the plant species dispersed by endozoochory lack a fleshy fruit and have previously been assigned to other dispersal syndromes, mainly associated with wind (10%), self-dispersal (22%) or epizoochory (18%). Plants lacking a fleshy fruit were particularly well-represented from the Caryophyllaceae (12 species), Poaceae (14 species), and Polygonaceae (8 species). Of 27 taxa germinated by Heintze from seeds extracted from corvid pellets or feces (71% of those tested), 20 lack a fleshy fruit. Similarly, of 32 taxa he recorded as seedlings having germinated from pellets in the field, 11 lacked a fleshy fruit. However, Heintze's quantitative data show that classical endozoochory is dominant in Magpies Pica pica and Hooded Crows Corvus cornix, for which 97% of seeds dispersed were fleshy-fruited. Corvids overlap with waterfowl as vectors of terrestrial plants dispersed by non-classical endozoochory, and 56 species are dispersed by both corvids and dabbling ducks according to the lists of Heintze and Soons et al. (2016). Finally, Heintze's data show that corvids were already dispersing alien plants in Europe a century ago, such as the North American Dwarf Serviceberry Amelanchier spicata.

- by Andy Green and +1
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- Seed Dispersal, Frugivory and seed dispersal, Corvids, Mutualism

Nature is composed of self-propelled, animate agents and inanimate objects. Laboratory studies have shown that human infants and a few species discriminate between animate and inanimate objects. This ability is assumed to have evolved to support social cognition and filial imprinting, but its ecological role for wild animals has never been examined. An alternative, functional explanation is that discriminating stimuli based on their potential for animacy helps animals distinguish between harmless and threatening stimuli. Using remote-controlled experimental stimulus presentations, we tested if wild jackdaws (Corvus monedula) respond fearfully to stimuli that violate expectations for movement. Breeding pairs (N ¼ 27) were presented at their nests with moving and non-moving models of ecologically relevant stimuli (birds, snakes and sticks) that differed in threat level and propensity for independent motion. Jackdaws were startled by movement regardless of stimulus type and produced more alarm calls when faced with animate objects. However, they delayed longest in entering their nest-box after encountering a stimulus that should not move independently, suggesting they recognized the movement as unexpected. How jackdaws develop expectations about object movement is not clear, but our results suggest that discriminating between animate and inanimate stimuli may trigger information gathering about potential threats.

- by Alison L Greggor
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- Animal Cognition, Corvids, Corvidae, Animacy / Inanimacy

Food-storing corvids use many cache-protection and pilfering strategies. We tested whether Eurasian jays (Garrulus glandarius) reduce the transfer of auditory information to a competitor when caching and pilfering. We gave jays a noisy and a quiet substrate to cache in. Compared with when alone, birds cached less in the noisy substrate when with a conspecific that could hear but could not see them caching. By contrast, jays did not change the amount cached in the noisy substrate when they were with a competitor that could see and hear them caching compared with when they were alone. Together, these results suggest that jays reduce auditory information during caching as a cache-protection strategy. By contrast, as pilferers, jays did not attempt to conceal their presence from a cacher and did not prefer a silent viewing perch over a noisy one when observing caching. However, birds vocalized less when watching caching compared with when they were alone, when they were watching a non-caching conspecific or when they were watching their own caches being pilfered. Pilfering jays may therefore attempt to suppress some types of auditory information. Our results raise the possibility that jays both understand and can attribute auditory perception to another individual.

- by Nicky S Clayton
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- Social Cognition, Animal communication, Corvids, Biological Sciences

Bresgunova O.A. About the diet of the Magpie (Pica pica) and Rook
(Corvus frugilegus) in winter time. – The results of investigation of the Magpie and
Rook diet by pellets which they regurgitate at communal roost sites was discussed.

- by Olga Bresgunova
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- Ornithology, Corvids, Corvidae

To the question of using of Eurasian Magpies’ (Pica pica) nests by other animals. Several observations of the using of Eurasian Magpies’ nests for roosting by other animals in Kharkiv region were presented. Common Chiffchaff... more

- by Olga Bresgunova
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- Ornithology, Corvids, Corvidae
- by John Scanlon
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- Vertebrate Evolution, Historical Biogeography, Corvids, Noise

State-attribution is the ability to ascribe to others an internal life like one's own and to understand that internal, psychological states such as desire, hope, belief, and knowledge underlie others' actions. Despite extensive research, comparative studies struggle to adequately integrate key factors of state-attribution that have been identified by evolutionary and developmental psychology as well as research on empathy. Here, we develop a behavioral paradigm to address these issues and investigate whether male Eurasian jays respond to the changing desire-state of their female partners when sharing food. We demonstrate that males feed their mates flexibly according to the female's current food preference. Critically, we show that the males need to see what the female has previously eaten to know what food she will currently want. Consequently, the males' sharing pattern was not simply a response to their mate's behavior indicating her preference as to what he should share, nor was it a response to the males' own desire-state. Our results raise the possibility that these birds may be capable of ascribing desire to their mates. corvid | Theory of Mind | cooperation | specific satiety I n human development, the earliest manifestation of state-attribution is the ability to explain and predict others' behavior in terms of desire-states (e.g., wants, wishes, hopes), a capacity that does not require a concept of others' mental representations (1, 2). At around the age of four, the more complex desire-belief system is formed by incorporating the attribution of epistemic mental states (e.g., belief, knowledge, doubt, expectation) (3, 4), an ability known as Theory of Mind. It is very possible that the attribution of desire-states may represent not only the developmental, but also the evolutionary, precursor of Theory of Mind. Thus, the first logical step in the investigation of state-attribution in nonhuman animals should be to search for this simpler manifestation (5). Despite this, most comparative studies focus solely on the attribution of epistemic mental states (6-13).

- by Lucy Cheke
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- Theory of Mind, Social behavior in animals, Animal Cognition, Corvids

Theory suggests that the balance between unknown dangers and novel opportunities drives the evolution of species-level neophobia. Juveniles show lower neophobia than adults, within mammals and birds, presumably to help minimize the costs of avoiding beneficial novelty, and adults tend to be more neophobic, to reduce risks and focus on known stimuli. How these dynamics function in island species with fewer dangers from predators and toxic prey is not well understood. Yet, predicting neophobia levels at different age classes may be highly valuable in conservation contexts, such as species' trans-location programmes, where responses to novelty can influence the effectiveness of prerelease training and animals' survival postrelease. To better understand how neophobia and its age-related patterns are expressed in an island corvid, we surveyed object neophobia in 84% of the world's critically endangered 'alal a, Corvus hawaiiensis. Individuals repeatedly demonstrated high neophobia, suggesting that neither captivity nor their island evolution has erased this corvid-typical trait. Unexpectedly, juveniles were exceedingly more neophobic than adults, a pattern in stark contrast to common neophobia predictions and known mammalian and avian studies. We discuss the potential conservation ramifications of this age-structured result within the larger context of neophobia theory. Not only may the expression of neophobia be more complicated than previously thought but predicting such responses may also be important for conservation management that requires exposing animals to novelty.

- by Alison L Greggor
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- Corvids, Animal Behaviour and Biodiversity Conservation, Neophobia

Many corvid species accurately remember the locations where they have seen others cache food, allowing them to pilfer these caches efficiently once the cachers have left the scene [1]. To protect their caches, corvids employ a suite of different cache-protection strategies that limit the observers’ visual or acoustic access to the cache site 2 and 3. In cases where an observer’s sensory access cannot be reduced it has been suggested that cachers might be able to minimise the risk of pilfering if they avoid caching food the observer is most motivated to pilfer [4]. In the wild, corvids have been reported to pilfer others’ caches as soon as possible after the caching event [5], such that the cacher might benefit from adjusting its caching behaviour according to the observer’s current desire. In the current study, observers pilfered according to their current desire: they preferentially pilfered food that they were not sated on. Cachers adjusted their caching behaviour accordingly: they protected their caches by selectively caching food that observers were not motivated to pilfer. The same cache-protection behaviour was found when cachers could not see on which food the observers were sated. Thus, the cachers’ ability to respond to the observer’s desire might have been driven by the observer’s behaviour at the time of caching.

- by Ljerka Ostojic and +3
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- Animal Behavior, Theory of Mind, Animal Cognition, Corvids

A communal roost of Magpie Pica pica, in a park in the southern part of Sofia
(W Bulgaria), was studied between the end of September 2007 and the middle
of April 2008. The roost-site of the Magpies was in a thicket of deciduous and
coniferous trees, up to 6 m high, in a natural dip in the relief, well protected
from the wind and from human interference. The number of birds in the
roost reached its maximum in February, with a peak of 724 birds on 21 Feb
2008. Their departure from the park with the roost site, started at an average
31.24 ± 8.3 min before sunrise, continued for 23.4 ± 4.4 min, and ended
at an average 7.8 ± 6.4 min before sunrise. The beginning of the departure
period was significantly earlier (U = 4, p < 0.05) and the duration of the period
significantly longer (U = 20.5, p < 0.05) after the start of breeding attempts
at the beginning of February. The average evenness index of departure (after
Levins) was 8.16 ± 4.4 and its values were significantly higher after the start of
breeding attempts, corresponding to more even departure from the park (U =
13, p < 0.05). The between-days dynamics of the departure showed that most
birds flew off in the second third of the daily departure period, but significantly
more Magpies took off in the last third of the departure period after the start
of breeding attempts. The opposite is true for the period before the breeding
attempts.

- by Boyan Milchev
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- Corvids, Roost Ecology, Communal Roosting
- by Olga Bresgunova
- •
- Ornithology, Corvids, Corvidae, Roosting behaviour

THE ORGANIZATION OF THE HOODED CROW (CORVUS CORNIX) COMMUNAL ROOSTS IN KHARKOV
O.A.Bresgunova
I investigated the peculiarities of sea．sonal organization of the Hooded crow (Corvus cornix) communal roost sites in Kharkov city in 2003-2005. The Hooded crows form small (several hundred individuals) roosting aggregations from April on traditional territories. These roosting locations exist several months and roost sites are contiguous with preroosting territories. From the middle October crows begin to leave these roosting sites and move into remote traditional combined communal roost. This huge winter congregation may include 4500 individuals. The catchment radius of roost is at least 15-16 km. Our data indicates that the crows’ numbers on the large communal roost appreciably declined from the middle of March, though some individuals keep together on this territory until the beginning of April. On this territory the communal roosts of the Black-billed Magpies (from 30 to 150 depending on the period of the year), Rooks and Jackdaws (the maximal numbers in the middle of November and in the end of February) are located also.

- by Olga Bresgunova
- •
- Ornithology, Corvids, Corvidae, Roosting behaviour

Peculiarities of breeding biology of the Magpie in Kharkiv region.
The study was carried out on three plots in 2002–2007 (two plots within Kharkiv city and one
plot in the flood-plain of Siverskiy Donets river). Magpies build nests since early March till mid April. 13.3%
of pairs prefer to repair old nests. Building of new nests lasts from 18 to 30 days, on average 27 days (n = 20).
In the city magpies start egg laying 10 days earlier than at Siverskiy Donets river. The full clutch has from 1 to
9 eggs, on average 6.5 (n = 65). Incubation lasts 24 days. Fledging usually lasts about 27–30 days. Hatching is
asynchronous and as a results smallest nestlings died because of siblicide. The breeding success of
Magpies was described and discussed. The breeding pair produced on average 1.6 fledglings, the successfull pair
– 3.5. The main cause of nest destruction is predation. The anti-predator behaviour of parents and their offspring
is described.

- by Olga Bresgunova
- •
- Ornithology, Corvids, Corvidae

Understanding causal regularities in the world is a key feature of human cognition. However, the extent to which nonhuman animals are capable of causal understanding is not well understood. Here, we used the Aesop's fable paradigm -in which subjects drop stones into water to raise the water level and obtain an out of reach reward -to assess New Caledonian crows' causal understanding of water displacement. We found that crows preferentially dropped stones into a water-filled tube instead of a sand-filled tube; they dropped sinking objects rather than floating objects; solid objects rather than hollow objects, and they dropped objects into a tube with a high water level rather than a low one. However, they failed two more challenging tasks which required them to attend to the width of the tube, and to counter-intuitive causal cues in a Ushaped apparatus. Our results indicate that New Caledonian crows possess a sophisticated, but incomplete, understanding of the causal properties of displacement, rivalling that of 5-7 year old children.

- by Lucy Cheke
- •
- Cognitive Science, Associative Learning and Memory, Tool-Use, Corvids