A regurgitated corvid food pellet

Although owls and birds of prey are best known for regurgitating pellets of indigestible prey fragments, other birds - including herons, gulls and members of the crow family - also produce similar but smaller pellets.

This one, which I found on a fence post today, was most likely produced by a crow, magpie or jackdaw. At the front of the pellet you can see a crane-fly wing.

If you look closely you can see that much of it is made up of chitinous fragments of insect exoskeleton. There are broken pieces on what look like beetle elytra in there but are also crustacean remains, in the form of the tail segments of a wood louse (the white material just above the centre of the picture).