To spot the goldcrests, bull finches, robins, thrushes, blackbirds, wrens and house sparrows in my small group of native trees requires patience and a willingness to drift into daydream. They flit through the trees with agility, slipping in and out of sight, wishing to remain unseen.
The same cannot, however, be said for the ever-expanding mob of invasive grey squirrels, who bound from branch to branch with astonishing confidence, swinging through the trees like acrobats, except with the grace of elephants tiptoeing through daisies. The young trees reverberate under their weight, accompanied by the screeches of outraged rooks, crows, jackdaws and magpies, who seem to resent the grey squirrels scurrying ceaselessly around the place almost as much as I do.
The squirrels are unbothered and relaxed under my gaze. In recent weeks, I’ve been watching rather obsessively as they spend an inordinate amount of time on the ground, moving in staccato bursts while deftly stuffing nuts and acorns into small, shallow holes, just a few inches deep, with their dexterous front paws. Some of these caches are just a few inches apart, carpeting the soil under the trees with a mosaic of scattered seeds.
When they’re not hiding the seeds away, the squirrels nibble at fallen apples (the trees are laden with fruit this year), undeterred by the challenge of tackling large, outsized apples – they lightly cradle these big specimens between their paws, rotating them as they skim off the peel with their teeth and eat a thin layer of flesh underneath.
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It’s proving to be a bumper autumn for nuts, and my young oak trees have produced a prodigious crop of acorns. It’s a time of feast, not famine, and such bounty signals a “mast year”, which comes around every couple of years. During these mast years, trees in the beech family (oaks, sweet chestnuts, beeches) and hazels release seeds in astonishing profusion, covering the forest floor with potential new life.
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The acorn is a tiny treasure chest, encased by a tough, hard exterior, full of bitter-tasting tannins to deter predators, which guards the valuable contents inside: a jewel of a seed, surrounded by starchy reserves that will keep a nascent tree alive as it grows. Full of protein, fats and carbohydrates, acorns are essential for woodland life – mice, squirrels, jays and badgers in particular – especially in the depths of winter, when little else food-wise is on offer. Cracking the shell might take a lot of energy and effort, but the energy-rich rewards inside are worth it.
Mast years are still something of an enigma. They are natural, biological events, but are somewhat unpredictable and involve trees acting in unison. Why? And how do they do it? A prevailing theory is that by producing a flood of seeds all at once, trees overwhelm the appetites of their predators and ensure that at least some seeds will survive and grow.
Oaks aren’t making seeds to feed the creatures in the wood; their aim is to spread their genes through reproduction. In a mast year, with so many acorns falling to the ground – too many for the predators around to eat – a percentage are guaranteed to take root. Had every year been a mast year, the forest would be overrun by predators who would devour nearly every seed, and the trees’ chance to reproduce would vanish.
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Scientists still aren’t entirely sure how trees co-ordinate their efforts across hundreds of miles. Weather conditions, of course, play a role. Oaks are wind-pollinated: the male catkins release their pollen into the spring air, hoping to reach the smaller female flowers. A warm, dry spring like this year’s – Ireland’s warmest and sunniest on record and the 16th driest since 1941 – encourages greater pollen production and germination, and sets the stage for a bumper seed crop.
In a mast year, a single mature oak can shed 10,000–20,000 acorns, which exacts a toll on the tree, and this strain leaves its mark deep within the oak’s trunk. The energy it spends making acorns instead of growing is recorded as narrow rings. In the years between mast events (next year might well see a sparse acorn crop of about 2,000 per mature tree), the tree puts more resources into growth, and the rings widen. It’s either growth of acorns, or growth of the tree.
The mast year unfolding in my small stand of trees is a boon for the creatures that rely on seeds for food this coming winter. Fortunately, the grey squirrels can be a bit forgetful, and about 10 per cent of the acorns they bury will go undiscovered. Vexing and irritating as the squirrels may be, if a few oak saplings appear in the soil next year, all will be forgiven.
