‘Cheap’ filler ingredients in bird feed are harming your garden birds – ingredient red flags to look out for, according to wildlife experts

Wildlife experts are warning gardeners against leaving ‘cheap’ suet balls in their bird feeders this January, due to the risk they contain filler ingredients that can be harmful to birds.

If you’re someone who tries to attract birds to your garden, no doubt feeding them has become part of your routine - and it is a truly joyful experience. Knowing what and when to feed birds not only encourages them to keep visiting your garden and provides natural pest control and pollination services, but also keeps our feathered friends safe, healthy and well-fed.

However, experts have revealed that some suet products contain less-than-desirable ingredients, such as chalk, which can be very harmful to birds. Here’s everything you need to look out for, as well as the suet balls the experts recommend.

The warning

If you’ve been wondering what to feed birds in winter, suet balls are a great option. Rich in fat, they are a valuable source of energy for birds, helping them maintain their weight when food is scarce. Did you know that in winter, some small birds can expend up to 10% of their body weight in a single night in an effort to keep warm?

However, in cheaper suet balls, ‘filler’ ingredients are added to bulk up the product. This means that birds are receiving less nutritional feed, and in some cases, are exposed to dangerous ingredients.

‘Filler’ products are surprisingly common in low-quality bird food, and it’s crucial to be aware of any additions, like sawdust, wheat, cracked corn, or red milo. Unfortunately, they’re often used to bulk out suet balls and reduce manufacturing costs - ingredients like sawdust and excessive amounts of cheap grains allow for heavier products and cheaper production,’ says James Ewens, gardening and wildlife expert from Green Feathers.

‘It can potentially be harmful for our feathered friends, but equally, fillers are not nutritious for birds, and without them, birds would be consuming much healthier, nutrient-dense foods per gram.’

What filler ingredients do you need to avoid?

One increasingly popular ‘filler’ ingredient is chalk, which offers no nutritional benefit and is even considered harmful to birds.

‘Sawdust does occasionally appear in very cheap suet products, but in truth, it’s fairly uncommon these days. What is becoming increasingly common is something far more worrying: calcium carbonate – essentially chalk,’ says Danny Yeoman, Wild Bird Expert for Pets Corner and developer of Peter & Paul Wild Bird Foods.

‘Calcium carbonate is extremely cheap – often costing less than £100 per metric tonne – and is added in large quantities simply to bulk suet balls out. In these amounts, it provides no nutritional benefit whatsoever to birds. The birds can’t derive meaningful calcium from it, and it doesn’t supply the fat or energy they desperately need. Frankly, the companies using it might as well be adding builders’ dust for all the good it does.

‘Even more concerning is the use of chemical hardeners such as PVA glue. These are added to disguise the fact that there isn’t much actual suet in the product. PVA is cheap, binds dry ingredients together well, and helps the balls hold their shape – but we simply don’t know the long-term impact that repeated consumption of PVA may have on wild bird populations. That uncertainty alone should make us very cautious.’

How to check for filler products

While this all sounds a little worrying, it is possible to check the ingredients of suet balls before you purchase them, ensuring that your garden birds are getting the best meals possible.

‘Always check the ingredient lists, you are looking for products where wheat flour, suet/tallow/fats and oils are the main ingredient with additions such as peanuts, sunflowers or other seeds such as millet, black rapeseed and linseed,’ advises James Jaques, Product Development Manager at The RSPB.

‘Cheaper products will often be darker in colour due to poorer quality beef suet/tallow used. They will also be really hard to the touch but easy to crumble into hundreds of pieces due to the addition of calcium carbonate.’

The gold rule is that if a product looks too good to be true, it probably is. And for the welfare of your garden wildlife, it is worth spending a little extra on high-quality feeds.

What to feed birds

‘I’d always recommend high-quality suet products made with clearly listed, bird-safe ingredients and no fillers. Look for suet balls that use pure beef suet or lard combined with nutritious additions like sunflower hearts or seeds,’ says James.

‘My favourite way to guarantee there’s no fillers is to make bird food myself. It’s easier than you think to make high-energy, highly nutritious food for birds, and making your own suet balls by heating beef suet or lard and adding any other nutritious goodies like sunflower hearts or seeds, or naked oats.’

It’s also a good idea to let your garden act as a natural bird buffet, too. Try bird-feeding plants so birds can forage for food in your garden all year round.

‘We sell our own bird food and can assure customers that we do not use any cheap fillers and are confident with the quality of the ingredients. So we would of course recommend our own suet products. As we haven’t reviewed the quality of other brands, we are not in a position to recommend them,’ says Charlotte Ambrose, RSPB Wildlife Expert.

Similarly, Danny developed his own bird feed range to put nutrition first and avoid cheap fillers.

‘Our products are made with proper, high-quality fats, blended with ingredients birds actually recognise and benefit from, such as insect meal and seeds. We do not bulk them out with chalk, sawdust or chemical binders. Every ingredient has a purpose, and that purpose is to support the health, energy and survival of garden birds,’ he says.

‘Putting food out for birds is an act of kindness, and it should genuinely help the wildlife we love watching in our gardens. By choosing suet products that prioritise nutrition over profit, we can make sure our feeders are a real lifeline and not just a filler,’ concludes Danny.

So, next time you go to pick up suet balls for your garden birds, take the time to look through the ingredients - your birds will thank you for it.