‘Robins ticked at him, wrens stittered.’
Perhaps another sound imitation coined by Williamson? His slim account of an otter’s joyous life and valiant death has a number of words evoking bird and otter sounds, several of which don’t occur in the OED’s 600,000 word hoard.
Here it’s clear that both robin and wren are threaping Tarka.
Source: Henry Williamson, Tarka the Otter: His joyful water-life and death in the two rivers, illus. C.F. Tunnicliffe (Harmondsworth: Puffin Books, 1976 (1927)), p. 212