seven steps you can try today

Frost creeps in, and wildlife faces a thirsty night. Gardeners across Britain are turning to an unlikely helper.

The first hard frosts arrive, water sources lock up, and small animals run short of safe places to drink. A simple household item can keep a gap in the ice and guide wildlife to it. Here is why a tennis ball makes a difference, who benefits, and how you can set it up in minutes.

Why a tennis ball works in frost

A floating tennis ball moves with the slightest breeze. That motion breaks the fragile ice crystals that first form on still water. The ball also absorbs a touch of daylight warmth and transfers it into the top film of water. Together, these effects keep a small window liquid when temperatures dip below zero.

In light frost, around −1 to −3°C, one ball can keep a 6–10 cm ring open on a bird bath or shallow tray. When the mercury falls lower, two balls increase the moving surface area and delay a solid freeze. On larger ponds, several balls spread across the surface can reduce the rate of icing overnight, especially if the pond sits out of strong, still air.

A moving float can preserve a drinkable gap as the temperature dips, buying hours that often decide survival.

Placement that gives results

Use a shallow, wide dish for birds and small mammals. A depth of 3–5 cm limits drowning risk and warms faster in the morning sun. Put the container near cover for quick retreat, but not right under a shrub where cats ambush. Two to three metres from dense cover strikes a fair balance.

Rinse an old ball first. Many dog-chewed balls shed fibres, so choose one with an intact, smooth surface. If wind is rare in your spot, tap the dish morning and evening to nudge the ball and break any thin film. Never smash thick ice on a pond with force. Shock waves can harm fish and amphibians.

Who benefits in your garden

Robins, blackbirds and tits use water through winter to drink and preen. Clean feathers insulate better, which reduces energy loss at night. Hedgehogs rouse from shallow torpor to feed and need water to digest dry food. Shrews, voles and even overwintering insects on mild days take quick sips, then dive back into cover.

Winter behaviours you can support

Short daylight cuts foraging time. Small birds lose mass fast after dusk. Ready water shortens their search and helps them hold energy. Hedgehogs that still roam in November or December may be underweight. Access to water next to a sheltered feeding point can lift their chances of making it through a cold snap.

Never offer milk to hedgehogs. Provide fresh water and meaty cat food if a hungry animal appears underweight.

Seven steps you can try today

Pick the right vessel: a 25–30 cm wide dish, 3–5 cm deep, with textured sides for grip.
Add the float: place one tennis ball for up to 0.25 m² of surface; two for 0.25–0.5 m².
Position well: set it 2–3 m from dense cover, on stable, level ground, away from busy paths.
Build an escape: lay a wooden ramp at roughly 30° into any container deeper than 10 cm.
Keep it clean: refresh every 48 hours. Scrub weekly with a 10% disinfectant solution, then rinse.
Check twice daily: crack thin ice gently with a wooden spoon, and remove slush. Never add salt, glycerine or antifreeze.
Combine support: leave leaf piles for shelter, reduce chemicals, and offer appropriate winter feed nearby.

Numbers that help you plan

Night temperature
Wind
Water surface
Balls to try
Typical ice-free gap

−1 to −3°C
Light breeze
Bird bath (25–30 cm)
1
6–10 cm ring

−3 to −5°C
Still
Bird bath or tray
2
4–6 cm patch

Below −5°C
Varies
Small pond (0.5–2 m²)
3–6 spaced
Intermittent gaps; manual checks needed

These figures are guides. Wind, sun, and vessel materials change outcomes. Morning checks remain vital in deep freezes.

Make it safe
Reduce hidden risks

Deep, steep-sided tubs can trap hedgehogs. Add a brick stair or coarse mesh to give firm footing. Avoid smooth metal bowls that chill water fast and are hard to grip. Place a low perch, such as a stick across the dish, so small birds land safely before drinking.

Hygiene matters in winter. Diseases spread quickly at busy water points. Wear gloves when cleaning. Rinse well. Let containers dry in the sun for an hour when possible. If local guidance warns of avian illness, change water more often and move the bath a few metres weekly to reduce contamination.

Fit an escape ramp or bricks in any container deeper than 10 cm. Simple hardware prevents drowning.

If you do not have a tennis ball

Use a ping-pong ball with a few grains of sand sealed inside to add inertia.
Tether a cork float to the rim with garden twine so wind keeps it moving.
Float a short length of untreated softwood; a rough surface resists icing.
Cut a disc of bubble wrap slightly smaller than the dish to reduce heat loss at the surface.
On larger ponds, a low-watt de-icer or an aeration stone can maintain one small opening.

Do not pour salt, ethanol, windshield fluid or any chemical into wildlife water. These substances dehydrate or poison animals and contaminate soil.

Small changes that stack up

Add shelter near the water. A knee-high heap of leaves, twigs and a few broken branches forms a dry core. Hedgehogs use such piles to rest, forage and hide. Keep bonfires unlit until you have moved the heap to check for hidden animals. Keep netting taut and at least 15 cm above ground to reduce entanglement.

Feed with purpose. Sunflower hearts, suet pellets and soaked sultanas suit many birds in freezing spells. Place small amounts and top up often to keep it fresh. For hedgehogs that still move, a tablespoon or two of meaty cat food at dusk next to water helps, then remove leftovers at dawn to deter pests.

Cost, energy and timing

A tennis ball costs about 99p and lasts a season if you rinse it often. If you opt for a heated bird bath during a severe freeze, a 25 W element running 12 hours uses roughly 0.3 kWh. At typical tariffs, that is around 10–12 p per day. Switch it on only during the coldest nights to limit cost and emissions.

Set a quick routine. Place the dish at dusk, check at breakfast, and again before dark. Refill with lukewarm water, not hot, to avoid cracking ceramic dishes. Rotate two containers so one is always clean and ready.

A cheap float, a clean dish and a daily check can keep wildlife hydrated when every sip counts.