Why native trees are the backbone of a bird-friendly wood

Walk into an old oak wood in late May and the noise is astonishing. Blue tits, great tits, blackcaps and chiffchaffs all singing at once, and beneath the song a steady rustle of caterpillars working through the canopy. That connection — native tree, insect, bird — is the whole engine of a British woodland. Nothing else in our landscape delivers as much for wildlife per square metre.

The reason is chemistry and time. Our native trees have been here for thousands of years, and the insects that feed on them have evolved alongside them. An English oak can support well over 280 species of caterpillar-carrying moth and butterfly, along with hundreds of aphids, gall wasps, beetles and sawflies. Birch, willow and hawthorn run it a close second. By contrast, most introduced trees — sycamore, sweet chestnut, horse chestnut, Turkey oak — carry a fraction of that insect load. A wood of handsome non-natives can look lovely and still be close to a desert for a brood of tits.

So if you own a few acres, manage a copse for a parish council, or simply plant a hedge along a field boundary, the mix of species you choose is the single most important decision you will make.

Spring and early summer: the caterpillar conveyor belt

Between late April and mid-June, a pair of blue tits will bring roughly 10,000 caterpillars to the nest. That is not a typo. They time their clutch precisely so the chicks hatch when oak, hawthorn and birch are at their most productive, and they will travel 50–100 metres from the nest to find the richest foliage.

To support that, you need:

• Mature oaks — nothing replaces an old tree. Even a single veteran oak in a hedge line is worth a hectare of new planting.
• Willow and birch — early to leaf, carrying moths that fill the gap before oak fully flushes.
• Alder and ash — useful for species in damp corners, particularly where the ground stays wet.
• Hawthorn, blackthorn and crab apple — superb for caterpillars and for the warblers that nest in their thorns.

Timing matters more than tidiness. Leave the scrub, leave the bramble, and never spray or flail the woodland edge in May.

Nesting: holes, forks and dense thickets

Different birds need different architecture. Great spotted woodpeckers, nuthatches and treecreepers depend on mature timber — soft standing deadwood for the woodpeckers to excavate, and deep-barked trunks for the treecreeper to spiral up. Marsh tits and coal tits nest in natural rot holes and old stumps. Lesser spotted woodpeckers, now desperately scarce, need dead limbs in full sun.

Warblers want the opposite: tangled, low, impenetrable growth. Willow warblers and garden warblers nest in coppice regrowth two to four years old, and in bramble and honeysuckle smothering the woodbank. Wrens, robins and dunnocks use the same messy corners.

Practically, that means:

• Leave at least a few standing dead trees per hectare — they are a habitat, not a hazard, if they are away from paths.
• Retain bramble and honeysuckle patches rather than grubbing them out.
• Stagger your coppicing so there is always a patch of one- to five-year-old growth.
• Keep a scatter of large, over-mature trees well beyond felling age.

Autumn and winter: seeds, berries and catkins

Winter is when native trees earn their keep again, this time as a larder. Siskins and lesser redpolls hang in alder and birch through January, working the small cones and catkins. Goldfinches strip birch and alder seed. Bullfinches take ash buds and hawthorn buds in late winter — a bird that will quietly strip a fruit tree in February. Fieldfares and redwings arrive for hawthorn, rowan and holly berries, and blackcaps overwinter increasingly on ivy berries.

Hazel, oak and beech provide the heavier mast that jays cache and woodpigeons strip. Woodpeckers will drum on dead branches and probe for overwintering insect larvae in bark crevices well into March.

If you are managing a wood for birds, resist the urge to tidy fallen mast or clear fallen timber. Leave some seed-bearing stems standing through the winter and take them out in March instead.

Planting and managing a mixed wood

If you are planting, work with bare-root whips between November and March, when the ground is workable and the trees are dormant. On most sites a spacing of 2–3 metres is fine, with a mix that leans heavily on the natives: roughly 40% oak, 20% birch, 15% willow, 15% hawthorn and blackthorn, and the remaining 10% made up of rowan, wild cherry, crab apple, hazel and alder in the damp hollows. Use tree guards or spiral guards where rabbits and deer are a problem, and mulch with a metre-wide mat to cut competition from grass.

Once established, the management is mostly restraint. Widen rides to at least 10 metres and scallop the edges so light reaches the ground. Maintain glades of a third to half an acre. Keep a minimum of 20% of the wood as long-term retention — the big old trees, the deadwood, the thickets — and put the rest on a rotation.

Ash dieback complicates things, but a proportion of ash will survive, and those trees are worth keeping and propagating from. Diversity is the insurance policy.

Reading the wood through the year

Keep a simple diary and the wood will tell you what it needs. Listen for woodpecker drumming in February and March — that tells you dead timber is still present. Watch for the first willow warblers and blackcaps in mid-April, arriving just as the caterpillars hatch. Note how many tit broods fledge in early June, and count siskins in the alders from December onwards.

If the woodland is loud in spring and busy in winter, you have got it right. If it is quiet, the answer is almost always more native trees, more deadwood and less tidying.