Common Ravens (Corvus corax)
Ravens are the largest songbirds on earth, weighing nearly 1.5 kg and with a wingspan of more than 1 metre. Their huge beak may serve to cut open carcasses, to hack off the wing of a mobbed conspecific, or to gently groom a social partner (including humans they are acquainted with) around eyes and ears. If geese may be called feathered primates because of their intricate sociality, ravens are the birdy equivalent of chimpanzees with respect to their (Machiavellian) intelligence.
It is our goal to investigate their abilities and how they use them. We believe that ravens are clever mainly because they co-evolved their cognitive skills as food parasites of large predators such as wolves, bears and humans. It is certainly demanding to divert prey from these animals without being killed. Secondly, they may use their cleverness in intra-specific competition for food, for mate choice and in other social interactions. Snatching food from potential predators would also explain why such potentially bright birds are at the same time prone to be highly neophobic. Their fear of almost anything makes it difficult to work with them and can be seen as constraint of cognitive abilities. The relationship between exploration and neophobia was at the focus of our previous work with ravens.
Comparable to geese, ravens are monomorphic and are long-term monogamous. However, contrary to geese, they only live in fission-fusion-groups during their first 3-8 years of life. After pair formation, a breeding territory is established and aggressively defended against conspecifics. Pairs show breathtaking aerial displays and can frequently be seen chasing other birds. They mob eagles and buzzards, they occasionally prey on smaller vertebrates and they may harass herons and other large, slow-flying birds, seemingly just for fun. Similar to humans and other primates, taking risks and being innovative may be an important mean by which mainly young males impress their potential partners.
The relatively stable aggregation of 40 (in summer) to 100 ravens (in winter) at the local Herzog von Cumberland Wildpark is caused by a stable food supply. Year long ravens participate in the feedings of the wolves and wild boars, where they divert considerable amounts. Particularly at the wolves a considerable risk is involved (5-10 ravens are killed there every year). An effect of the regular presence of observers is that these wild ravens are more approachable than most other groups of wild ravens in the world. The possibility to observe from a few metres distance benefits professional film teams documenting raven behaviour. Increasingly, some of these ravens are also individually marked by coloured leg rings and wing tags.
Although hand-raised ravens may make fascinating pets and companions, we strongly discourage hand-raising of single birds. Individuals raised within the family loose all their distance towards humans, may become a nuisance and even a danger for the neighbours, their children and pets and may even become aggressive towards people. Either such a raven is soon killed or locked into a small aviary.
Conditions during raising indeed determine whether or not individuals can be released and will integrate into a wild flock of wild ravens. For learning experiments, for example, individuals may be tailored during hand-raising in a way that they loose most of their neophobia. This is simply done by confronting birds with numerous situations and friendly people as nestlings and around fledging. However, for reasons discussed above, these animals cannot be released and need to be kept in adequate aviaries lifelong (which may be up to 40 years or longer).
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