If we could see it as a whole, if they all arrived in a single flock, say, we would be truly amazed: sixteen million birds.Swallows, martins, swifts, warblers, wagtails, wheatears, cuckoos, chats, nightingales, nightjars, thrushes, pipits and flycatchers pouring into Britain from sub-Saharan Africa.It is one of the enduring wonders of the natural world.Each bird faces the most daunting of journeys -navigating epic distances, dependent on bodily fuel reserves.Yet none can refuse. Since pterodactyls flew, twice-yearly odysseys have been the lot of migrant birds.For us, for millennia, the Great Arrival has been celebrated.From The Song of Solomon, through Keats' Ode To a Nightingale, to our thrill at hearing the first cuckoo call each year, the spring-bringers are timeless heralds of shared seasonal joy. Yet, migrant birds are finding it increasingly hard to make the perilous journeys across the African desert.Say Goodbye to the Cuckoo is a moving call to arms by an impassioned expert: get outside, teach your children about these birds, don't let them disappear from our shores and hearts.