This article first appeared in the The West Midland Bird Report for 1959.
Bird names/ spellings were used as given.
SOME NOTES ON THE GROWTH OF A ROOKERY
In 1931 a solitary pair of rooks reared young from a nest in a small wood near my house, the nearest rookery being half-a-mile away. Each year since I have counted the nests and numbers have been as follows: 3, 4, 5, 5, 15, 16, 12, 10, 3 (1940), 6, 8, 10, 14, 15, 18, 4 (1947), 7, 9, 21, 21, 30, 70 (1953), 78, 84, 61, 52, 57, 83 (1959).
Prolonged cold weather occurred during the early months of 1940 and 1947; that for 1940 began with an "ice-storm" on January 28th, when many boughs on trees were broken by the weight of ice formed upon them, oaks being the chief sufferers. Arctic conditions prevailed in 1947, when snow lay on the ground from January 22nd to March 16th, a period of 53 days, with a blizzard on March 4th, when snow drifted up to ten feet deep. In both these years the number of rooks' nests fell to a quarter that of the previous season, but nest building and incubation were not delayed; in fact, the rook is most regular in its time of breeding' and I have seen them incubating eggs with snow on their backs on several occasions. (On April 28th, 1945, half-an-inch of snow fell at 10 p.m. whilst a Nightingale sang vigorously!)
On May 12th, 1953, 134 young rooks were shot from the 70 nests by a neighbour who complained of damage done to his crops. If each nest had reared two young, then nearly the whole output of the rookery was destroyed. However, in the following year there were 78 nests, so the slaughter did not succeed in reducing this alleged pest. The rookery is in a wood consisting chiefly of oaks, with three small groups of ash trees in which most of the nests are built, and only a few oaks, which happen to be next the ash, are used. Until 1951 all the nests were in ash at the south end of the wood, but by 1959 the "grouping" had reached ash trees on the north side and consisted of 38-9-36 nests, of which 42 had been built by March 12th, and a few rooks' were incubating eggs.
The wood is on a very exposed hillside, and gales blow the nests about in the ash twigs far more than the few that are built in the wind-resistant tops of the oaks. One or two are blown down in most years, and on April 7th, 1943, half were destroyed by a gale; none of the rooks attempted repeat nests. During another gale a nest with well-feathered young in it landed right side up in an adjacent pasture. The parents fed their young in it for one-and-a-half days until a fox took them at night.
Rooks build their nests chiefly with new rather than dead sticks, as the former are more pliable. However, dead twigs are incorporated, and old magpies' nests are a favourite source and are often demolished within three days. If sticks are dropped en route to the nest, rooks don't bother to retrieve them, but fly on to the rookery with empty beaks, and of course one of the pair must remain at the nest site to prevent neighbours stealing all the sticks that have been collected.
Since 1947 1 have also counted the nests in a rookery in chestnut and lime trees adjacent to the Evesham churches in the centre of that town. The numbers have been 17, 34, 3, 10 (1950), 9, 14, 20, 16, 9 (1955), 21, 17, 14, 9 (1959). Here the rooks prefer the few chestnut trees rather than the more numerous limes. Live chestnut twigs are ripped off by the rook's beak as cleanly as if cut by secateurs.
A comparison between a small rookery in the country and one in a town over a number of years should provide much of interest to the bird-watcher with limited time, as the rooks' nesting activities can be seen so easily, and even, perhaps, at a glance from within a passing bus!
A. J. Harthan.
Ornithology in Staffordshire, Warwickshire, Worcestershire & the West Midlands county, since 1929.
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