Ranger's Blog reader Rachel Joyce has given a seasonal tip about fat balls. Yes, fat balls. Stop sniggering at the back - and you Americans can stop snickering too if you were wondering.

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Peanuts and fat balls are regularly sold in nylon mesh bags. The RSPB advise that we should not put out bird food in mesh bags as they can trap birds' feet and even cause broken or torn off feet and legs. Birds with a barbed tongue, e.g. woodpeckers, can become trapped. So go and find something else to put your fat balls in. A suggestion is above, and you can buy something similar for only 70p here.

Rachel has set up a 10 Downing Street e-Petition to ban the sale of mesh-bagged bird food, you can sign it if you like. Seems like a reasonable idea.

But - hang on a moment - barbed tongues? What's all that about? A moment's research reveals that woodpeckers' tongues are indeed quite remarkable. The exceptionally long tongue actually wraps around the skull and is anchored at the base of the bill. The tip of the tongue is barbed to help extract insects from holes, and the tongue is coated with sticky saliva.

The woodpecker's tongue in action, showing it retracted and extended.

A reliable indication of a jolly interesting bit of biology can be found when something pops up regularly on Creationist websites as an example to demonstrate the futility of Darwinism. Woodpeckers' tongues seem to crop up fairly often, and given their remarkable properties it's hardly surprising. Whether many woodpeckers actually peck at fat balls is less certain, but just to be on the safe side, go and get yourself a safe fat ball holder and the woodpeckers can peck your balls with impunity.