An Explanation

We've had possibly the widest variety of birds in the garden today.  I've recently added another feeder with premium seed and well as a coconut shell with fat.  We're now seeing more sparrows and tits in the garden, as well as a rarely seen wren.

This image might explain why some of the chaffinches can't grip onto the feeder with sunflower hearts.  Here you can see that the claws are affected by scaly leg or tassel foot, a very common affliction.  This bird was also seen perching on branches of the tree, but seemingly lying on its belly, rather than standing above on its legs.  I can only assume it has very little use of the legs to stand or grip with.