Recent reports of the sighting of four rooks on coastal farmland near Matauri Bay not far from Whangarei has alarmed the Northland Regional Council as the birds, considered by some people to be very destructive, have not been seen in the region before.
Many people do not realise we have rooks in New Zealand. We do not see these birds in the Eastern Bay of Plenty but the rook does have the ability to disperse widely from known breeding areas, especially juveniles, so it is as well for bird watchers to be alert.
The last time I saw rooks was in the northern Wairarapa on my sister’s farm under the Ruahine mountain range not far from Ekatahuna. There, the open rolling landscape, shaped by dairy farms with shelter belts of old macrocarpa trees (Monterey cypress) and Lombardy poplars, seems to attract few birds other than the more common introduced birds, many magpies, and rooks. The eastern Rosella, which is there in quite large numbers, is the brightest spot in an otherwise dull avian landscape.
The rook is a black, hoarse–voiced bird about the size of a magpie which was brought to New Zealand from Britain between 1862 and 1874 to help control insects and to remind settlers of home. Unlike many other European birds introduced at the same time, rooks have spread very slowly. Even as late as 1970, they were largely confined to parts of the Hawke’s Bay, Manawatu, southern Wairarapa and Canterbury.
The rooks belong to the family Corvidae which includes crows and jays and are among the more intelligent birds. Their natural breeding range is Europe and Asia, east Siberia and Mongolia. Many migrate south to winter around the Mediterranean, in Iran and the northern part of the Indian sub continent.
Rooks like areas where there are walnut trees and agricultural crops, especially cereals. They avoid the bush and forested areas so are no real threat to our native or endemic birds. They prefer to eat insects, earthworms and walnuts but when these become scarce the birds may gather in large flocks and eat maize, wheat, barley, peas or beans.
The habit of storing walnuts is of special interest. Ripening nuts are picked from a tree and carried some distance and buried intact in open paddocks, in a tuft of grass or between clods of ploughed soil. The birds return in autumn to recover the stored nuts, which they hold on the ground with one foot while hammering a hole through the hard shell to extract the kernel.
The social organization of these remarkable birds is very complex. Rooks are gregarious, not only when feeding together but also breeding and roosting together.
In late August, nests are built in the tops of very tall trees such as poplars and pines. Several nests may be within a few metres of each other and large rookeries may contain several hundred nests. The nest is large and untidy and is made of twigs, leaves and mud and lined with grass. The female incubates the bluish green eggs blotched with brown and is fed by the male while brooding.
During winter, up to 5000 or more birds from several breeding rookeries will travel up to 20 kilometres each night to roost together at a large or long established rookery, called “parishes”. In the morning they disperse to feeding grounds around their own rookeries.
The ornithologist W.H.R. Oliver reports, “When the young can fly they accompany their parents on bird–nesting expeditions, the victims being mostly sparrows, whose nests they tear to pieces, devouring the eggs or young to the accompaniment of the most ecstatic cawing.” This habit, he says, was welcomed because it was thought to help keep sparrow numbers under some control. He also says they are not at all attracted to our native forests and when they first appear in a district are readily chased away by magpies.
My Scottish friends tell me that “rook pie” is an excellent dish. Apparently the Scots were in the habit of shooting young birds before they quite flew the nest, skinning them to take just the breasts for the pie.
In the 1971 rooks were declared an agricultural pest in the Hawke’s Bay and something like 35,000 thousand were shot, probably about half the population. Displaced rooks then spread more rapidly and established colonies near Miranda, Tolaga Bay near Gisborne and southern Waikato among other places including Northland.
