Crows match many primates on a brain-to-body score
The crow-and-raven genus Corvus holds about forty-six species on every continent except South America and Antarctica. Lab work since 2002 shows some not only wield tools but fashion them, with encephalization scores beside many non-human primates.
Corvus, Latin for raven, covers the crows, ravens, and rooks. Linnaeus named the genus in 1758 with the common raven as its type, and today it holds some 42 living species plus at least 14 extinct ones, about a third of the whole crow family. In Europe the later-discovered species were labelled crow or raven mostly by size. They range from small Mexican crows of 34 cm to common and thick-billed ravens of 60 to 70 cm, among the biggest songbirds. The genus probably spread from Central Asia around 10 million years ago, and its greatest variety is in New Guinea, Melanesia, and Wallacea.
Intelligence is their fame. New Caledonian crows pluck, smooth, and bend twigs into foraging tools, as tail-mounted cameras showed in 2007. Hooded crows in Israel use breadcrumbs as fishing bait, Queensland crows flip toxic cane toads to eat the safe innards, and crows in a Yokohama park work drinking fountains. Crows recognise individual human faces, and ravens recognise themselves in mirrors.
Ravens form partnerships with wolves: in winter they are with wolf packs almost all the time, calling predators to injured elk and feeding on the kills, sometimes eating more than the wolves. Crows mob great horned owls, which prey on them, with loud calls and dive-bombing.
Crows eat almost anything, from nuts, seeds, and earthworms to eggs, mice, and carrion, which is why farmers invented scarecrows, though the birds also eat crop pests. Outside the breeding season they gather in roosts of 200 to tens of thousands, often near rubbish dumps and shopping centres.
Source: Corvus
