Why a sudden cold snap is deadly for garden birds

British winters are becoming more unpredictable, and it is often the short, sharp cold snaps rather than the long, steady frosts that catch our garden birds out. A small bird such as a blue tit or wren can lose a significant proportion of its body weight during a single freezing night. With daylight hours reduced to just eight or nine, every moment of the day must be spent finding food, and every calorie counts. Natural sources — berries, seeds, insects and grubs — are locked away under frost or snow just when they are needed most. That is where a well-stocked garden becomes a genuine lifeline. Feeding birds in winter is not simply a pleasant hobby; it is practical conservation, and doing it well makes a real difference to survival rates.

Offer high-fat, high-energy foods

Not all bird food is equal. In cold weather, birds need calories in the most concentrated form possible, which means fat. Suet, lard and vegetable fat are excellent, whether offered as fat balls, suet blocks or homemade cakes. Choose fat balls without the plastic mesh netting, which can trap small birds' feet and beaks, and use a proper feeder instead.

Other reliable winter staples include:

• Sunflower hearts — high in oil and fat, with no husk to discard, so they are quick to eat and leave no mess.
• Peanuts — rich in fat and protein, but always buy plain, unsalted and guaranteed free from aflatoxin. Never put out salted or dry-roasted nuts.
• Mealworms — dried or live, and particularly valuable for robins, wrens and blue tits. Soak dried mealworms in warm water first to make them easier to digest.
• Nyjer seed — a favourite of goldfinches and siskins, best offered in a specialist feeder with tiny ports.
• Mixed seed — good for ground feeders such as dunnocks and chaffinches, but check that the mix is fresh and not bulked out with cheap fillers like split peas or lentils.

What should you avoid? Bread is poor value and can fill a bird up without nourishing it; mouldy food can be toxic; and anything salty, sugary or cooked in oil is best left out of the feeder entirely.

Keep feeders and tables scrupulously clean

Winter feeding brings birds together in unnaturally close quarters, and that is exactly how diseases such as trichomonosis and avian pox spread. A dirty feeder is worse than no feeder at all. Clean your feeders every fortnight at the very least — weekly during a cold snap when more birds are visiting. Dismantle them fully, scrub every part with hot soapy water and a bottle brush, rinse thoroughly, then allow them to dry completely before refilling.

A few simple habits make a big difference:

• Rotate feeding stations and move them slightly every few weeks to prevent a build-up of droppings and spores in one spot.
• Discard any food that looks damp, clumped or mouldy, and never top up a feeder without checking what is underneath.
• Clean bird tables daily, and only put out as much food as will be eaten in a day.
• Wash your hands thoroughly after handling feeders, and keep a dedicated bucket and brush for the job.

Provide unfrozen water every day

It is easy to forget that birds need to drink and bathe even in freezing weather. A bird's feathers must be kept clean and well groomed to insulate properly, and a dip in unfrozen water helps them do that. On a hard frost, natural puddles and streams are sealed under ice. Check your bird bath or water dish every morning and break the ice, then top up with fresh water. Never pour boiling water directly into a bird bath, as the sudden heat can crack stone or ceramic and harm birds' feet.

A simple trick is to float a small, clean ball or a piece of cork in the water; the movement helps stop it freezing over. Alternatively, a shallow dish placed in a sunny, sheltered spot will thaw more quickly. Whatever you use, keep it shallow — no more than five centimetres deep — with a gently sloping edge so birds can drink and bathe safely without risk of drowning.

Make feeding a reliable daily habit

Birds learn quickly where food is, and they will return to a reliable source again and again. That reliability matters: if you start feeding in November, try to keep going until spring, because birds will have incorporated your garden into their daily route. If you must stop, do it gradually rather than overnight.

Feed at the same times each day, ideally in the morning when birds are hungriest after a long, cold night, and again in the early afternoon to see them through the dark. Site feeders away from windows to reduce collisions, and close to dense shrubs or a hedge so that birds can retreat from a sparrowhawk. A little thought now will turn your garden into a genuine winter refuge — and you will be rewarded with the lively company of blue tits, blackbirds, goldfinches and, if you are lucky, a shy winter visitor or two.