Across British gardens this week, ice creeps over birdbaths while hungry hedgehogs stir and search for safe drinking spots.
As night temperatures dip to –3 to –7°C, a small, low-cost tweak can keep life-giving water accessible until dawn. Gardeners are turning to a humble bit of kit to hold the line against freeze-ups, buying precious hours for the creatures that share our plots.
A small ball, a big winter difference
A standard tennis ball floating in a shallow dish or small pond can disrupt ice formation, maintaining a fist-sized opening for wildlife to drink. Light gusts nudge the ball and stop a complete freeze. Even on still nights, the trapped air inside the ball acts as a modest insulator, and at first light you can lift it to expose a drinking hole without smashing ice.
One floating ball can keep a palm-sized hole open at –2 to –5°C, long enough for birds and hedgehogs to hydrate.
This isn’t a gimmick. Water is the critical winter shortage. Fat stores help animals survive the cold, but dehydration kills quickly. Keeping one or two access points open can tip the balance for species already battling short days and scarce food.
How the moving float delays icing
Ice forms fastest on still, shallow water. A floating object disrupts a uniform ice sheet, and any breeze keeps it shifting. Where a full crust forms, the ball is a ready-made “plug”: remove it and you have a safe gap for beaks and snouts. No chemicals, no power, no fuss.
Where to place it for best results
Choose a low, sheltered spot out of the strongest wind but with a clear line of sight so nervous birds feel safe. Depth matters. A 5–8 cm deep dish reduces drowning risk for small mammals. Place a rough stone or a stick ramp in the water so anything that falls in can climb out.
Who gains when water stays open
It’s not only garden regulars like robins and blackbirds. Winter-active small mammals and semi-dormant hedgehogs rouse for brief foraging and drink runs. Even on frosty mornings, you’ll see fleeting visits if you check from a window and stand back.
Hedgehogs and late-winter wake-ups
Hedgehogs typically hibernate, yet warm spells or low fat reserves can prompt wake-ups. When that happens, water is vital. Leave shallow access, never milk, and keep cat food offerings limited and protein-rich during cold snaps if you already support local hogs. Avoid deep-sided buckets and steep-edged tubs.
Birds need water as much as seed
Cold weather feeding helps, but birds also need liquid water for drinking and feather maintenance. Preening restores insulation; without it, heat loss accelerates. A small open patch lets robins, tits and thrushes sip safely and get back to cover quickly.
Never add salt, de-icer or antifreeze to wildlife water — a teaspoon can poison or kill.
Set-up in six quick steps
- Pick a shallow dish, 30–40 cm wide and 5–8 cm deep; add a stone or stick ramp.
- Fill with rainwater where possible; top up to about 2–3 litres to buffer overnight cooling.
- Float one tennis ball per 30 cm of surface area; add a second on larger trays.
- Site near cover but with clear approaches; avoid tight corners that trap animals.
- At dawn, if iced, lift the ball to reveal a drinkable hole; add a little warm (not boiling) water if needed.
- Clean every few days with hot water and a brush; rinse thoroughly before refilling.
Temperatures, time and risk: what to expect
Outcomes vary with exposure, humidity and wind. These rule-of-thumb figures help plan your routine on cold nights.
Light wind
Shallow dish, no float
With tennis ball
Plan a two-minute morning check on frosty days: lift the ball, refresh water, remove ice safely.
Make it safe
Water that helps should never become a trap. A few tweaks keep visitors out of trouble and predators at bay.
Avoid drowning hazards and ambush points
Use shallow containers, add a stable brick step or stick ladder, and roughen smooth rims with sand to give traction. Keep the station at least two metres from dense cover where cats can lurk, and avoid shiny surfaces that confuse birds at take-off.
Cleaning and disease control
Scrub algae with hot water and a dedicated brush. Skip detergents and harsh disinfectants. Rinse well, refill, and rotate the location every couple of weeks if droppings build up. Separate any pet bowls from wildlife water to reduce cross-contamination.
Why a tennis ball beats chemical shortcuts
Quick fixes like salt or de-icer harm kidneys and nervous systems in birds and mammals. Glycerine and alcohol are not safe either. Mechanical methods — balls, sticks, partial covers and timely warm-water top-ups — protect wildlife and avoid tainting the water source.
Beyond the ball: stack simple wins
The floating ball works best as part of a winter-friendly garden plan. Pair it with shelter and safe food to build resilience during cold snaps.
- Leaf piles and log stacks for invertebrates and hedgehog shelter.
- Mixed hedges and dense shrubs for windbreaks and quick cover.
- Seed heads left standing to feed finches and sparrows.
- No pesticides or slug pellets; hand-pick slugs and use barriers instead.
- Low night lighting; darkness helps nocturnal species move and feed.
Costs, minutes and impact
A used ball costs about 50p and installation takes three minutes. The pay-off is measurable: more morning visitors, fewer corpses after hard frosts, and a livelier soundscape on cold, bright days. Households on streets with several water points see steady traffic sharing the load, reducing predation around any single dish.
What to do on still, severe nights
When the air is dead calm and the thermometer plummets, add a second ball and place a lightweight twig tent over part of the dish to blunt radiative cooling. If ice wins, don’t hammer the surface — that can crack containers and stress wildlife. Pour a small kettle of warm (not boiling) water around the ball, lift it, and let visitors drink before refreezing sets in.
If you don’t have a tennis ball
A ping-pong ball, a cork bundle or a small, sealed plastic jar also works as a moving float. Avoid metal objects that conduct cold. The principle is the same: keep the surface busy, create a ready-made plug, and manage the morning routine.
For larger ponds, spread two or three floats across the surface and lay a stick raft near the edge so small mammals can clamber out. Where herons patrol, keep drinking spots shallow and separate from fish areas to prevent unintended baiting.
Think of the tennis ball as your night watch. It doesn’t heat or purify the water; it buys time and keeps access visible. Pair it with a safe ramp, regular cleaning, and a steady top-up schedule, and your plot becomes part of a neighbourhood safety net — one quiet, practical gesture at a time, through every frost from November to March.