Clever rooks play and learn in storms

Outdoor Living

SERVICE PROVIDERS Rooks help clear grassland of damaging leatherjackets, while their fruit-and-nut stashes help to regenerate our woodlands.

Country Sights and Sounds

John Shelley

Two days of high winds kept the rooks confined to barracks, to the tall trees where they were recently inspecting their nests and making needed repairs. Tidying around could hardly be the correct expression, for there is nothing at all tidy about the inverted mounds of sticks that comprise their homes, except perhaps the soft sheep’s-wool and horse-hair lining.
The nests might not be neat, but they are strong. Storm Ciara threw one or two to the ground; even after falling 40 feet and bouncing off branches on their way down these remain for the most part intact, though useless. More-experienced rooks build on the firm foundation offered by a cleft formed by diverging branches, and might use the same nest several years running, while younger pairs sometimes make several failed attempts at building before finally getting something to hold together.
During the storms the rook family had a ball, easily and rather joyously riding the gales. I stopped to watch them mid-morning while driving into town and again just on dusk, on my way back home, at which time they all seemed to be still there. They must have stopped for lunch, surely. On such windy days they seldom travel far.
The Latin name for the rook is Corvus frugilegus, Corvus denoting the crow family, to which also belong our colourful jays, the villainous magpie and the opportunistic Hooded or Greyback crow. Other Irish corvids include the raven, the jackdaw and the seldom seen but acrobatic, coast-dwelling chough.
The suffix frugilegus, the species name, means ‘food gatherer’, and refers to the rook’s habit of gathering surplus food and burying it in the ground somewhere else. To aid in this work the rook is equipped with a modified and elastic throat pouch, which is capable of carrying a good many acorns or other fruits.
The birds spend many days thus employed, collecting and concealing various foodstuffs, no doubt with the intention of retrieving the same at some future time of need. It seems they have but weak memories, and while they might recall the general area in which to search, actually finding the hidden cache requires much work.
In this way the rook unintentionally makes himself nature’s own forest grower, for even a small rookery of 40 of 50 birds must be capable of planting many thousands of acorns in a season. Some will be recovered, while others will be found by rats, mice or squirrels. Yet many acorns not reclaimed will germinate and sprout as the soil warms in spring, and a hundred years and four-score generations later more rooks will have more oaks to live in and work from. We would be covered with oak woods in no time.
Even locally I had been wondering at the appearance of oak seedlings along the shore of Lough Carra, where they struggle in the lime-rich soil. Here, though, I suspect jays have been at work, for they also help in what could be, were it allowed, a great replanting.
During a later lull in Ciara’s thundering tail I paused to watch the rooks feeding in a roadside field. There seemed no order, just a few dozen birds striding back and forth. I chose one and watched. A few steps in one direction were followed by ten in another before the bird stopped and turned its head on one side to examine the ground. It gave a hearty chuckle and stepped sideways, as if to gain a better vantage, then leaned forward and thrust its beak deep into the soil to claim its small prize, likely a leatherjacket, the larvae of the crane fly, which is so destructive to grassland.
Its morsel swallowed, the bird wandered along before repeating its action and claiming a second tidbit. I wrestled with a bit of mental arithmetic. If one rook eats three crane-fly larvae in one minute, how many larvae would 50 rooks eat in one 12-hour day, if only half that time were spent actively feeding?
Leatherjackets feed on grass roots and are hard to control. Up until 2016, certain pesticides could be used, but these harmful products are thankfully now banned across the EU. Biological control in the form of nematodes is available, although these are a bit ‘hit and miss’. The rooks are perfect for the job.
What fine birds they are! Restful, peaceable creatures, quietly and efficiently going about their work, rendering valuable service to all.