The birds are in their breeding colours. Or, as some describe it, their nuptial plumage. This morning, under a bright blue sky, the great tits are inspecting our nesting boxes, and as they pop in and out, their vivid colours flash on the garden’s late winter beige. They haven’t looked this good since last May – adult great tits start to moult even when they’re still feeding their young. The birds spend the rest of the year, drab and dull-looking. Today their black caps were particularly striking.