Ravens are adapting to change

RAVENS, according to a study in the US state of Idaho, are changing their behaviour. These huge crows used to live only around mountains, desert anyons and sea cliffs. Now they are nesting on phone masts, buildings and steel towers.

Over 73% of the nests found by Peter Coates, and colleagues of the US Geological Survey, were on man-made structures, 53% of them electricity pylons.

The team also studied the nesting choices of three species of buzzard. These, they found, were much less likely to change their ways. The red-tailed hawk is a bird you will see throughout the United States. Seventy per cent of the Idaho pairs nested in trees. Swainson’s hawks used traditional sites almost exclusively while over 74% of ferruginous hawks chose natural ones.

The research raises an interesting question: if ravens adapt to change so readily why can’t birds of prey do so? The raven is the world’s most widely distributed crow. Found throughout Europe Asia and North America, it features in folklore and mythology everywhere. The one Noah released from the Ark ‘went forth to and fro, until the waters were dried up from off the earth’. Odin’s two pet ravens flew everywhere, returning to tell him what they had seen. The goddess Morrigan, in the guise of a raven, followed Cuchulain; the bronze statue in Dublin’s GPO has her perching on the hero’s shoulder. If ravens ever leave the Tower of London, it’s said, Britain will be invaded.

The great black crow has a dark side; it frequented execution sites and battlefields to feed on corpses. Sheep farmers fear for their lambs; birds seen scavenging on carcasses, and carrying off afterbirths to feed to their young, have damaged the raven’s reputation. Sick or dying animals may be attacked but the authoritative Birds of the Western Palearctic states that ravens are ‘very unlikely’ to kill healthy lambs.

Crows are among the most intelligent of non-human creatures. The largest member of the family, a ‘Jack of all trades’, is an avian opportunist, able to turn its hand, or its bill, to almost anything. Ravens prefer meat but will eat almost anything. They raid nests for eggs and chicks, catch small animals, take molluscs from the seashore and scavenge on rubbish tips. If no animal food is available, fruit and cereals will suffice. This entrepreneurial spirit, the Idaho study shows, extends not just to food but to choice of nest location.

Hawks, in contrast, don’t live on their wits; coming from a line of hunters, they depend more on visual acuity speed and precision-targeting for their survival. Human activity is changing the Idaho landscape, reducing the availability of the creatures on which predators traditionally depended, rendering finely-tuned hunting methods increasingly redundant. When it comes to nesting, the raptors seem equally ‘set in their ways’; innovation isn’t in their blood. Adapt or die, the businessman advises; wild creatures must do likewise. Ravens cope well with the huge environmental changes we have brought about. The species has thrived both here and in North America over the last four decades. The hawks, perhaps, are faring less well.

Nor are Irish ravens dragging their feet. Half a century ago, seeing or hearing one was a bit special. There were no nests in several inland counties. When more enlightened attitudes towards birds of prey and scavengers developed, the opportunist ravens colonised the lowlands, nesting in quarries and tall trees. According to the Bird Atlas, the British and Irish breeding range has increased by 68% since 1970. The winter range expanded by 79% since 1984.

The contention that raptors are slow to adapt to change isn’t really borne out here. Sparrowhawks hunt in suburban gardens and peregrines now nest in lowland quarries. A pair raised chicks for several years on Dublin’s huge gas tower, now demolished.