Corvidae
Corvids Temporal range:
| |
---|---|
Blue jay Cyanocitta cristata | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Passeriformes |
Superfamily: | Corvoidea |
Family: | Corvidae Leach, 1820 |
Genera | |
See text | |
Distribution map of the Corvidae.
Native (Re)Introduced Extinct (post-1500) Extinct (pre-1500)
|
Corvidae is a cosmopolitan family of oscine passerine birds that contains the crows, ravens, rooks, magpies, jackdaws, jays, treepies, choughs, and nutcrackers.[1][2][3] In colloquial English, they are known as the crow family or corvids. Currently, 135 species are included in this family. The genus Corvus containing 47 species makes up over a third of the entire family.[4] Corvids (ravens) are the largest passerines.
Corvids display remarkable
They are medium to large in size, with strong feet and bills, rictal bristles, and a single moult each year (most passerines moult twice). Corvids are found worldwide, except for the southern tip of South America and the polar ice caps.[3] The majority of the species are found in tropical South and Central America and in southern Asia, with fewer than 10 species each in Africa and Australasia. The genus Corvus has re-entered Australia in relatively recent geological prehistory, with five species and one subspecies there. Several species of raven have reached oceanic islands, and some of these species are now highly threatened with extinction, or have already become extinct.
Systematics, taxonomy, and evolution
The name Corvidae for the
Clarification of the interrelationships of the corvids has been achieved based on
The
Corvidae |
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Fossil record
The earliest corvid fossils date to mid-Miocene Europe,[16] about 17 million years ago; Miocorvus and Miopica may be ancestral to crows and some of the magpie lineage, respectively, or similar to the living forms, due to convergent evolution. The known prehistoric corvid genera appear to be mainly of the New World and Old World jay and Holarctic magpie lineages:
- Miocorvus (Middle Miocene of Sansan, Gers in southwestern France)
- Miopica (Middle Miocene of SW Ukraine)
- Miocitta (Pawnee Creek Late Miocene of Logan County, US)
- Corvidae gen. et sp. indet. (Edson Early Pliocene of Sherman County, Kansas, USA)[17]
- Protocitta (Early Pleistocene of Reddick, US)
- Corvidae gen. et sp. indet. (Early/Middle Pleistocene of Sicily) – probably belongs in an extant genus
- Henocitta (Arredondo Clay Middle Pleistocene of Williston, US)
In addition, there are numerous fossil species of extant genera since the Mio–Pliocene, mainly European Corvus.[a]
Morphology
Corvids are large to very large passerines with a robust build and strong legs; all species, except the pinyon jay, have nostrils covered by bristle-like feathers.[18] Many corvids of temperate zones have mainly black or blue coloured plumage; however, some are pied black and white, some have a blue-purple iridescence, and many tropical species are brightly coloured. The sexes are very similar in color and size. Corvids have strong, stout bills and large wingspans. The family includes the largest members of the passerine order.
The smallest corvid is the dwarf jay (Aphelocoma nana), at 41 g (1.4 oz) and 21.5 cm (8.5 in). The largest corvids are the common raven (Corvus corax) and the thick-billed raven (Corvus crassirostris), both of which regularly exceed 1,400 grams (3.1 pounds) and 65 cm (26 in).
Species can be identified based on size, shape, and geography; however, some, especially the
Ecology
Corvids occur in most climatic zones. Most are sedentary, and do not migrate significantly. However, during a shortage of food, irruptive migration can occur.[2] When species are migratory, they will form large flocks in the fall (around August in the Northern Hemisphere) and travel south.[19]
One reason for the success of crows, compared to ravens, is their ability to overlap breeding territory. During breeding season, crows were shown to overlap breeding territory six times as much as ravens. This invasion of breeding ranges allowed a related increase in local population density.[20]
Since crows and magpies have benefited and even increased in numbers due to human development, it was suggested that this might cause increased rates of nest predation of smaller bird species, leading to declines. Several studies have shown this concern to be unfounded. One study examined American crows, which had increased in numbers, were a suspect in nest predation of threatened marbled murrelets. However, Steller's jays, which are successful independently of human development, are more efficient in plundering small birds' nests than American crows and common ravens. Therefore, the human relationship with crows and ravens did not significantly increase nest predation when compared to other factors, such as habitat destruction.[20] Similarly, a study examining the decline of British songbirds found no link between Eurasian magpie numbers and population changes of 23 songbird species.[21]
Behaviour
Some corvids have strong organization and community groups. Jackdaws, for example, have a strong social hierarchy, and are facultatively colonial during breeding.[22] Providing mutual aid has also been recorded within many of the corvid species.
Young corvids have been known to play and take part in elaborate social games. Documented group games follow "king of the mountain" or "follow the leader" patterns. Other play involves the manipulation, passing, and balancing of sticks. Corvids also take part in other activities, such as sliding down smooth surfaces. These games are understood to play a large role in the adaptive and survival ability of the birds.[23]
Mate selection is quite complex, and accompanied with much social play in the Corvidae. Youngsters of social corvid species undergo a series of tests, including aerobatic feats, before being accepted as a mate by the opposite sex.[19]
Some corvids can be aggressive. Blue jays, for example, are well known to attack anything that threatens their nest. Crows have been known to attack dogs, cats, ravens, and birds of prey. Most of the time, these assaults take place as a distraction long enough to allow an opportunity for stealing food.[19]
Food and feeding
The natural diet of many corvid species is omnivorous, consisting of invertebrates, nestlings, small mammals, berries, fruits, seeds, and carrion. However, some corvids, especially the crows, have adapted well to human conditions, and have come to rely on human food sources. In a US study of American crows, common ravens, and Steller's jays around campgrounds and human settlements, the crows appeared to have the most diverse diet of all, taking anthropogenic foods, such as: bread, spaghetti, fried potatoes, dog food, sandwiches, and livestock feed. The increase in available human food sources is contributing to population rises in some corvid species.[20]
Some corvids are predators of other birds. During the wintering months, corvids typically form foraging flocks., and since they lack a specialized beak for tearing into flesh, they must wait until animals are opened, whether by other predators or as roadkill.
Reproduction
Many species of corvid are territorial, protecting territories throughout the year, or simply during the breeding season. In some cases, territories may only be guarded during the day, with the pair joining off-territory roosts at night. Some corvids are well-known communal roosters. Some groups of roosting corvids can be very large, with a roost of 65,000 rooks counted in Scotland.[24] Some, including the rook and the jackdaw, are also communal nesters.
The partner bond in corvids is extremely strong, and even lifelong in some species. This monogamous lifestyle, however, can still contain extra-pair copulations.[25] Males and females build large nests together in trees or on ledges; jackdaws are known to breed in buildings and in rabbit warrens.[22] The male will also feed the female during incubation.[26] The nests are constructed of a mass of bulky twigs lined with grass and bark. Corvids can lay between 3 and 10 eggs, typically ranging between 4 and 7. The eggs are usually greenish in colour with brown blotches. Once hatched, the young remain in the nests for up to 6–10 weeks depending on the species.
Corvids use several different forms of parental care, including
Intelligence
It has been suggested that this section be split out into another article titled Corvid intelligence. (Discuss) (July 2023) |
Jerison (1973) has suggested that the degree of brain
Their intelligence is boosted by the long growing period of the young.[33][34][35] By remaining with the parents, the young have more opportunities to learn necessary skills.
When compared to dogs and cats in an experiment testing the ability to seek out food according to three-dimensional clues, corvids out-performed the mammals.
Empathy-consolation
Ravens are found to show bystander affiliation, and solicited bystander affiliation after aggressive conflicts.[39] Most of the time, bystanders already sharing a valuable relationship with the victim are more likely to affiliate with the victim to alleviate the victim's distress ("consolation") as a representation of empathy. Ravens are believed to be able to be sensitive to other's emotions.
Empathy-emotional contagion
Interspecific communications
Personality conformity
It is considered difficult to study emotions in animals when humans could not communicate with them. One way to identify animal
Social construction
The individual personality is both determined by genetics and shaped by
Social complexity
The social complexity hypothesis suggests that living in a social group enhances the cognitive abilities of animals. Corvid ingenuity is represented through their feeding skills, memorization abilities, use of tools, and group behaviour. Living in large social groups has long been connected with high cognitive ability. To live in a large group, a member must be able to recognize individuals, and track the social position and foraging of other members over time. Members must also be able to distinguish between sex, age, reproductive status, and dominance, and to update this information constantly. It might be that social complexity corresponds to their high cognition, as well as contributing to the spread of information between members of the group.[49]
Consciousness, culture-rudiments, and neurology
The Eurasian magpie is the only non-mammal species known to be able to recognize itself in a mirror test,[50] although later research could not replicate this finding.[51] Studies using very similar setups could not find such behaviour in other corvids (e.g., Carrion crows[52][53]). Magpies have been observed taking part in elaborate grieving rituals, which have been likened to human funerals, including laying grass wreaths.[54] Marc Bekoff, at the University of Colorado, argues that it shows that they are capable of feeling complex emotions, including grief.[54] Furthermore, carrion crows show a neuronal response that correlates with their perception of a stimulus, which some scientists have argued to be an empirical marker of (avian/corvid) sensory consciousness—the conscious perception of sensory input—in the crows which do not have a cerebral cortex.[55][56] A related study shows that the birds' pallium's neuroarchitecture is reminiscent of the mammalian cortex.[57][58]
Tool use, memory, and complex rational thought
There are also specific examples of corvid cleverness. One carrion crow was documented cracking nuts by placing them on a crosswalk, letting the passing cars crack the shell, waiting for the light to turn red, and then safely retrieving the contents.[59] A group of crows in England took turns lifting garbage bin lids while their companions collected food.
Members of the corvid family have been known to watch other birds, remember where they hide their food, then return once the owner leaves.[60][61] Corvids also move their food around between hiding places to avoid thievery—but only if they have previously been thieves themselves (that is, they remember previous relevant social contexts, use their own experience of having been a thief to predict the behavior of a pilferer, and can determine the safest course to protect their caches from being pilfered). Studies to assess similar cognitive abilities in apes have been inconclusive.[62]
The ability to hide food requires highly accurate
New Caledonian crows (Corvus moneduloides) are notable for their highly developed tool fabrication. They make angling tools of twigs and leaves trimmed into hooks, and then subsequently use the hooks to pull insect larvae from tree holes. Tools are engineered according to task, and apparently, also to learned preferences. Recent studies revealed abilities to solve complicated problems, which suggested high levels of innovation of a complex nature.[63][64] Other corvids that have been observed using tools include: the American crow, blue jay, and green jay. Researchers have discovered that New Caledonian crows do not just use single objects as tools—they can also construct novel compound tools through assemblage of otherwise non-functional elements.[65][66] Diversity in tool design among corvids suggests cultural variation. Again, great apes are the only other animals known to use tools in such a fashion.[3]
Clark's nutcrackers and jackdaws were compared in a 2002 study based on geometric rule learning. The corvids, along with a domestic pigeon, had to locate a target between two landmarks, while distances and landmarks were altered. The nutcrackers were more accurate in their searches than the jackdaws and pigeons.[67]
Implications and specific comparisons with other animals
The scarecrow is an archetypal scare tactic in the agricultural business. However, due to corvids' quick wit, scarecrows are soon ignored, and used as perches. Despite farmers' efforts to rid themselves of corvid pests, their attempts have only expanded corvid territories, and strengthened their numbers.[19]
Contrary to earlier
During the 19th century, there arose the belief that these were the "most advanced" birds, based upon the belief that Darwinian evolution brings "progress." In such a classification, the "most intelligent" of birds were listed last, reflecting their position "atop the pyramid." Modern biologists reject the concept of hierarchical "progress" in evolution [...].[2]
The other major group of highly intelligent birds of the order
) is not closely related to corvids.A study found that four-months-old ravens can have physical and social cognitive skills similar to that of adult great apes, and concluded that the "dynamic of the different influences that, during ontogeny, contributes to adult cognition" is required for the study of cognition.[69][68]
Disease
Corvids are reservoirs (carriers) for the West Nile virus in the United States. They are infected by mosquitoes (the vectors), primarily of the Culex species. Crows and ravens are quickly killed by this disease, so their deaths are an early-warning system when West Nile virus arrives in an area (as are horses and other bird-species deaths). One of the first signs that West Nile virus first arrived in the US in 1999 was the death of crows in New York.[70]
Relationship with humans
Several different corvids, particularly
It is illegal to own corvids, or any other
Humans have been able to coexist with many members of the Corvidae family throughout history, most notably
Role in myth and culture
Folklore often represents corvids as clever, and even mystical, animals. Some Native Americans, such as the Haida, believed that a raven created the earth, and despite being a trickster spirit, ravens were popular on totems, credited with creating man, and considered responsible for placing the Sun in the sky.[71]
Due to their
Various
The sixth century BCE Greek scribe Aesop featured corvids as intelligent antagonists in many fables. Later, in western literature, popularized by American poet Edgar Allan Poe's work "The Raven", the common raven becomes a symbol of the main character's descent into madness.
The children's book Mrs. Frisby and the Rats of NIMH and its animated film adaptation features a protagonist crow named Jeremy.
Status and conservation
Unlike many other bird families, corvid fitness and reproduction, especially with many crows, has increased due to human development. The survival and reproductive success of certain crows and ravens is assisted by their close relationship with humans.[20]
Human development provides additional resources by clearing land, creating shrublands rich in berries and insects. When the cleared land naturally replenishes, jays and crows use the young dense trees for nesting sites. Ravens typically use larger trees in denser forest.[20]
Despite the fact that most corvids are not threatened (many even increasing due to human activity) a few species are in danger. For example, the destruction of the Southeast Asian rainforest is endangering
The
Species
FAMILY CORVIDAE
- Choughs
- Genus Pyrrhocorax
- Alpine chough, Pyrrhocorax graculus
- Red-billed chough, Pyrrhocorax pyrrhocorax
- Genus
- Treepies
- Genus Crypsirina
- Hooded treepie, Crypsirina cucullata
- Racket-tailed treepie, Crypsirina temia
- Genus Dendrocitta
- Andaman treepie, Dendrocitta bayleii
- Bornean treepie, Dendrocitta cinerascens
- Grey treepie, Dendrocitta formosae
- Collared treepie, Dendrocitta frontalis
- White-bellied treepie, Dendrocitta leucogastra
- Sumatran treepie, Dendrocitta occipitalis
- Rufous treepie, Dendrocitta vagabunda
- Genus Platysmurus
- Malayan black magpie, Platysmurus leucopterus
- Bornean black magpie, Platysmurus aterrimus
- Genus Temnurus
- Ratchet-tailed treepie, Temnurus temnurus
- Genus Crypsirina
- Oriental magpies
- Genus Cissa
- Common green magpie, Cissa chinensis
- Indochinese green magpie, Cissa hypoleuca
- Javan green magpie, Cissa thalassina
- Bornean green magpie, Cissa jefferyi
- Genus Urocissa
- Taiwan blue magpie, Urocissa caerulea
- Red-billed blue magpie, Urocissa erythroryncha
- Yellow-billed blue magpie, Urocissa flavirostris
- Sri Lanka blue magpie, Urocissa ornata
- White-winged magpie, Urocissa whiteheadi
- Genus Cissa
- Old World jays and close relatives
- Genus Garrulus
- Eurasian jay, Garrulus glandarius
- Black-headed jay, Garrulus lanceolatus
- Lidth's jay, Garrulus lidthi
- Genus Podoces– ground jays
- Xinjiang ground jay, Podoces biddulphi
- Mongolian ground jay, Podoces hendersoni
- Turkestan ground jay, Podoces panderi
- Iranian ground jay, Podoces pleskei
- Genus Ptilostomus
- Piapiac, Ptilostomus afer
- Genus Zavattariornis
- Stresemann's bushcrow, Zavattariornis stresemanni
- Genus Garrulus
- Nutcrackers
- Genus Nucifraga
- Spotted nutcracker, Nucifraga caryocatactes
- Kashmir nutcracker, Nucifraga multipunctata
- Clark's nutcracker, Nucifraga columbiana
- Genus
- Holarctic magpies
- Genus Pica
- Black-billed magpie, Pica hudsonia
- Yellow-billed magpie, Pica nuttalli
- Eurasian magpie, Pica pica
- Korean magpie, Pica (pica) serica
- Genus Cyanopica
- Azure-winged magpie, Cyanopica cyanus
- Iberian magpie, Cyanopica cooki
- Genus Pica
- True crows (crows, ravens, jackdaws and rooks)
- Genus Corvus
- Australian and Melanesian species
- Little crow, Corvus bennetti
- Australian raven, Corvus coronoides
- Bismarck crow, Corvus insularis
- Brown-headed crow, Corvus fuscicapillus
- Bougainville crow, Corvus meeki
- Little raven, Corvus mellori
- New Caledonian crow, Corvus moneduloides
- Torresian crow, Corvus orru
- Forest raven, Corvus tasmanicus
- Relict raven, Corvus (tasmanicus) boreus
- Grey crow, Corvus tristis
- Long-billed crow, Corvus validus
- White-billed crow, Corvus woodfordi
- Pacific island species
- ʻAlalā (Hawaiian crow), Corvus hawaiiensis (formerly Corvus tropicus) (extinct in the wild)
- Mariana crow, Corvus kubaryi
- Tropical Asian species
- Daurian jackdaw, Coloeus dauuricus
- Slender-billed crow, Corvus enca
- Palawan crow, Corvus pusillus[78]
- Flores crow, Corvus florensis
- Large-billed crow, Corvus macrorhynchos
- Eastern jungle crow, Corvus levaillantii
- Indian jungle crow, Corvus culminatus
- House crow, Corvus splendens
- Collared crow, Corvus torquatus
- Piping crow, Corvus typicus
- Banggai crow, Corvus unicolor
- Eurasian and North African species
- Hooded crow, Corvus cornix
- Mesopotamian crow, Corvus (cornix) capellanus
- Carrion crow (western carrion crow), Corvus corone
- Eastern carrion crow, Corvus (corone) orientalis
- Rook, Corvus frugilegus
- Western jackdaw, Coloeus monedula
- Fan-tailed raven, Corvus rhipidurus
- Brown-necked raven, Corvus ruficollis
- Hooded crow, Corvus cornix
- Holarctic species
- Common raven, Corvus corax (see also next section)
- extinctcolor variant)
- Common raven, Corvus corax (see also next section)
- North and Central American species
- American crow, Corvus brachyrhynchos
- Northwestern crow, Corvus brachyrhynchos caurinus
- Chihuahuan raven, Corvus cryptoleucus
- Tamaulipas crow, Corvus imparatus
- Jamaican crow, Corvus jamaicensis
- White-necked crow, Corvus leucognaphalus
- Cuban crow, Corvus nasicus
- Fish crow, Corvus ossifragus
- Palm crow, Corvus palmarum
- Sinaloa crow, Corvus sinaloae
- Western raven, Corvus (corax) sinuatus
- American crow, Corvus brachyrhynchos
- Tropical African species
- White-necked raven, Corvus albicollis
- Pied crow, Corvus albus
- Cape crow, Corvus capensis
- Thick-billed raven, Corvus crassirostris
- Somali crow (dwarf raven), Corvus edithae
- Australian and Melanesian species
- Genus
- Boreal jays
- Genus Perisoreus
- Canada jay, Perisoreus canadensis
- Siberian jay, Perisoreus infaustus
- Sichuan jay, Perisoreus internigrans
- Genus Perisoreus
- New World jays
- Genus Aphelocoma – scrub-jays
- California scrub jay, Aphelocoma californica
- Island scrub jay, Aphelocoma insularis
- Woodhouse's scrub jay, Aphelocoma woodhouseii
- Florida scrub jay, Aphelocoma coerulescens
- Mexican jay, Aphelocoma wollweberi
- Transvolcanic jay, Aphelocoma ultramarina
- Unicolored jay, Aphelocoma unicolor
- Genus Calocitta– magpie-jays
- Black-throated magpie-jay, Calocitta colliei
- White-throated magpie-jay, Calocitta formosa
- Genus Cyanocitta
- Blue jay, Cyanocitta cristata
- Steller's jay, Cyanocitta stelleri
- Genus Cyanocorax
- Black-chested jay, Cyanocorax affinis
- Purplish-backed jay, Cyanocorax beecheii
- Azure jay, Cyanocorax caeruleus
- Cayenne jay, Cyanocorax cayanus
- Plush-crested jay, Cyanocorax chrysops
- Curl-crested jay, Cyanocorax cristatellus
- Purplish jay, Cyanocorax cyanomelas
- White-naped jay, Cyanocorax cyanopogon
- Tufted jay, Cyanocorax dickeyi
- Azure-naped jay, Cyanocorax heilprini
- Bushy-crested jay, Cyanocorax melanocyaneus
- White-tailed jay, Cyanocorax mystacalis
- San Blas jay, Cyanocorax sanblasianus
- Violaceous jay, Cyanocorax violaceus
- Green jay, Cyanocorax luxuosus
- Inca jay, Cyanocorax yncas
- Yucatan jay, Cyanocorax yucatanicus
- Genus Psilorhinus
- Brown jay, Psilorhinus morio
- Genus Cyanolyca
- Silvery-throated jay, Cyanolyca argentigula
- Black-collared jay, Cyanolyca armillata
- Azure-hooded jay, Cyanolyca cucullata
- White-throated jay, Cyanolyca mirabilis
- Dwarf jay, Cyanolyca nanus
- Beautiful jay, Cyanolyca pulchra
- Black-throated jay, Cyanolyca pumilo
- Turquoise jay, Cyanolyca turcosa
- White-collared jay, Cyanolyca viridicyanus
- Genus Gymnorhinus
- Pinyon jay, Gymnorhinus cyanocephalus
- Genus Aphelocoma – scrub-jays
Explanatory notes
- ^ See the genus accounts for more.
- Icelandic: hrafnaguð, as per the Gylfaginning.
References
- ^ ISBN 978-1-873403-18-1.
- ^ a b c d e f Robertson, Don (30 January 2000): Bird Families of the World: Corvidae Archived 28 April 2006 at the Wayback Machine. Retrieved 2007-NOV-10.
- ^ PMID 15694292.
- Rasmussen, Pamela, eds. (January 2023). "Crows, mudnesters, birds-of-paradise". IOC World Bird List Version 13.1. International Ornithologists' Union. Retrieved 15 May 2023.
- S2CID 9828891.
- ^ "Rooks reveal remarkable tool-use". BBC News. 26 May 2009. Retrieved 2 April 2010.
- ^ Birding in India and South Asia: Corvidae. Retrieved 2007-NOV-10
- ^ Leach, William Elford (1820). "Eleventh Room". Synopsis of the Contents of the British Museum. Vol. 17 (17th ed.). London: British Museum. pp. 67–68. The name of the author is not specified in the document.
- hdl:2246/830.
- PMID 21262814.
- ^ S2CID 85317440.
- .
- ISBN 0-565-00979-6
- doi:10.1046/j.1474-919X.2003.00170.x. Archived from the original(PDF) on 17 December 2008. Retrieved 10 November 2007.
- .
- S2CID 86482094.
- JSTOR 1363487.
- ISBN 0-19-852506-0
- ^ a b c d e Shades of Night: The Aviary Archived 15 April 2006 at the Wayback Machine. Version of 2004-JUL-21. Retrieved 2007-NOV-10.
- ^ .
- PMC 1689492.
- ^ S2CID 53199764.
- ISBN 0-7167-2415-4
- JSTOR 2402685.
- S2CID 34041075.
- Encyclopædia Britannica Online: Corvidae. Free subscription required.
- PMID 16777726.
- PMID 24686934.
- PMID 24132311.
- ISBN 978-0-12-385250-2, retrieved 11 March 2021
- ISBN 978-1-4613-4717-0, retrieved 11 March 2021
- PMID 16553307.
- ^ "Long childhoods and extended parenting help young crows grow smarter". phys.org. Retrieved 2 July 2020.
- S2CID 225766325.
- PMID 32475334.
- PMID 112801.
- ^ Rincon, Paul (22 February 2005) Crows and jays top bird IQ scale. BBC.
- S2CID 9828891.
- PMID 20485685.
- PMID 30002482.
- PMID 31110007.
- PMID 17118930.
- .
- ISSN 0021-8790.
- PMID 11271756.
- PMID 20638151.
- )
- PMID 26848954.
- S2CID 9836564. Archived from the original(PDF) on 16 February 2008. Retrieved 10 November 2007.
- PMID 18715117.
- S2CID 218636079.
- S2CID 218976227.
- S2CID 203850271.
- ^ a b Animal emotions, wild justice and why they matter: Grieving magpies, a pissy baboon, and empathic elephants Archived 10 June 2015 at the Wayback Machine Emotion, Space and Society xxx (2009) 1–4, Marc Bekoff
- ^ "Researchers show conscious processes in birds' brains for the first time". phys.org. Retrieved 9 October 2020.
- S2CID 221881862. Retrieved 9 October 2020.
- ^ Stetka, Bret. "Bird Brains Are Far More Humanlike Than Once Thought". Scientific American. Retrieved 23 October 2020.
- S2CID 221882087. Retrieved 16 October 2020.
- ^ "Attenborough – Crows in the City". YouTube.com. 12 February 2007. Archived from the original on 7 November 2021. Retrieved 9 March 2013.
- JSTOR 4086793.
- S2CID 86971311.
- National Geographic News, Retrieved 2007-NOV-10.
- ^ Morelle, Rebecca (20 April 2010). "BBC On-line: Clever New Caledonian crows can use three tools". BBC News. Retrieved 9 March 2013.
- ^ Baraniuk, Chris (12 December 2020). "Crows could be the smartest animal other than primates". BBC. Retrieved 31 August 2020.
- PMID 30356096.
- ^ Starr, Michelle (25 October 2018). "Crows Can Build Compound Tools Out of Multiple Parts, And Are You Even Surprised". ScienceAlert. Retrieved 4 April 2020.
- PMID 12539930.
- ^ .
- ^ "Cognitive performance of four-months-old ravens may parallel adult apes". phys.org. Retrieved 17 January 2021.
- PMID 11585521.
- ^ "Raven Releasing the Sun". Native Online. Retrieved 30 July 2020.
- JSTOR 25477680. Retrieved 20 September 2022 – via JSTOR.
- PMC 1326277.
- .
- .
- ISBN 978-0-300-10076-1.
- ^ "Species Updates – IOC World Bird List". Retrieved 29 May 2021.
Further reading
- ISBN 0-300-04085-7.
External links
- Corvidae videos on the Internet Bird Collection
- corvids.de – Corvids-Literature-Database
- Corvid Corner A site about the Corvidae
- AvesNoir A site about corvids in art, culture, and literature.
- Discovery of species-wide tool use in the Hawaiian crow
- Rooks reveal remarkable tool use
- Clever New Caledonian crows can use three tools
- Talking Eurasian magpie Pica pica
- Rare crow shows a talent for tool use