The raven: a primate of the sky?
Ravens are large songbirds with a circumpolar distribution in the Northern hemisphere. Since ancient times, they have attracted the human's attention and got the reputation of being tricky and smart. In the scientific literature, there exist also numerous anecdotes on the ravens' intelligence. Yet, experimental evidence for those claims is scarce.
Ravens are opportunistic scavengers assembling in non-kin groups on ephemeral carcasses or kills, but also use food supplies in game parks or at garbage dumps. By recruiting conspecifics at nocturnal roosts and via food-calls, ravens may overcome the food defence of dominant conspecifics or may increase their safety when co-feeding with potential predators such as wolves. Group formation, however, may also lead to increased competition among individuals. Presumably as a consequence, ravens repeatedly carry off food and scatter-hoard at a moderate distance to the commonly used feeding site. Ravens not only remember their own caches but also those they have seen others make and routinely use this skill for pilfering others' caches. Thus, individuals use a variety of tactics to gain, and keep food safe, from conspecifics which apparently creates a need for developing sophisticated socio-cognitive skills.
The kea: Clever clown of the mountains
The kea, Nestor notabilis, is generally believed to be one of the most intelligent birds. New Zealand is full of anectodes about the extraordinaire behaviour of these birds (as e.g. tearing the nose of a mountaineer biwaking beside a glacier). Its exploratory, curiosity and play behaviour are most conspicuous. Beside these and some other key features of the kea's biology, it is its almost complete lack of neophobia that makes this species especially attractive for cognitive investigations not only in the lab but also in the field. This neophilia may have evolved under the special circumstances of a harsh habitat on a eyeland wit a lack of predators.
The kea is one of six native parrot species of New Zealand . This olive-green parrot with bold orange-red under wing coverts is one of the few parrot species with sexual dimorphism: males have longer bills and are heavier (960 g average) than females (780 g). It is endemic to the South Island where about 3000-5000 kea live in the mountain areas of southern beech (Nothofagus) forest, sub-alpine scrub and alpine grassland. No other parrot species occurs at such high altitudes throughout the whole year, even when there is snow during winter.
There they forage on more than 100 species of plants and insects: they feed on fruits and seeds from trees, bushes and grass, and nectar from flowers. They dig for roots of grass and herbs and catch insects. They feed on carcass and rubbish. About 150'000 keas were shot during the last 100 years because some keas attack and feed on live sheep. Since 1986 kea are fully protected by the government.
Compared to the kea's closest relative, the kaka, Nestor meridionalis, that inhabits lower altitude temperate forests, the kea has an extended juvenile period. After up to six months sixteen weeks of full dependence on their parents, young kea aggregate in social flocks until they form breeding pairs at the age of 4 to 5 years.
Thus, the kea fulfils many conditions that are believed to favor cognitive abilities: extended parental association, potentially long life span, group foraging, opportunism, curiosity and extreme iteroparity.
For people interested in reading more about the general biology of this explorative and playful parrot, we recommend the book by Judy Diamond and Alan Bond from the University of Nebraska:
The budgie, short for budgerigar (Melopsittacus undulatus), is a parrot species that is native to Australia, and prefers a dry desert climate. Wild budgies are nomadic, and follow rainfall to find fresh grass seeds. However, they have been brought over to Europe, bred, and kept as pets for over one hundred years.