Calci worms are one of the fastest growing choices in bird feeding, and for good reason. Here is what they are, which birds love them, and exactly when to use them.
What are calci worms?
Calci worms are the dried larvae of the black soldier fly. Despite the name, they are not worms at all, but a soft, grub-like larva that garden birds take to readily. Their stand out quality is calcium: they are one of the most calcium rich natural foods you can offer wild birds, alongside a healthy dose of protein.
Why calcium matters for garden birds
Calcium is essential for strong bones and, crucially, for eggshell formation during the breeding season. A female bird laying a clutch needs a large amount of calcium in a short space of time, and a shortfall can lead to thin shelled or failed eggs. Growing chicks need calcium too, to develop healthy bones. That is what makes calci worms so valuable from spring right through summer.
Which birds eat calci worms?
A wide range of garden birds enjoy them, including robins, blackbirds, tits, wrens, sparrows, thrushes and finches. Robins in particular are known for taking calci worms readily, often becoming bold enough to feed while you are still nearby. Because calci worms are soft and small, they are also easier for newly fledged birds to manage than firmer foods.
Calci worms vs mealworms
This is the question we are asked most often. Both are excellent, but they do different jobs. Mealworms are higher in protein and fat, which makes them a dense energy food, especially valued through winter. Calci worms are higher in calcium, which makes them the priority during the breeding season.
The ideal approach is to offer both, either mixed in the same dish or side by side. For a full breakdown, read our guide to mealworms vs calci worms.
How to feed calci worms
Offer them in a bird table dish, a hanging feeder or a ground feeder. You can feed them dry, or soak them briefly in warm water to soften them, which is particularly helpful during nesting season. Keep portions modest, provide fresh water nearby, and always keep feeders and dishes clean to protect visiting birds.
Good news for hedgehog friendly gardens: if hedgehogs visit, calci worms are a better choice than mealworms. Mealworms in any quantity can interfere with a hedgehog's calcium absorption, whereas calci worms are far kinder to them.
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