Meet Chris - a totally new kind of cuckoo clock One of the most memorable scenes in the movies occurs in the Graham Greene-Carol Reed drama of occupied post-war Vienna, The Third Man, made in 1949, when Orson Welles" Harry Lime, a small-time criminal who has been making a fortune from selling contaminated penicillin which has been killing children in hospitals, chides his long-lost friend Holly Martins (played by Joseph Cotten) for his humanitarian scruples. Lime/Welles tells Martins/Cotten: "In Italy, for 30 years under the Borgias they had warfare, terror, murder and bloodshed, but they produced Michelangelo, Leonardo da Vinci, and the Renaissance. In Switzerland, they had brotherly love - they had five hundred years of democracy and peace, and what did that produce? The cuckoo clock. It is doubtful if any timepiece has ever been so unfavourably immortalised (with Welles rumoured to have added the words to the script himself). But if we move away from considering cuckoo clocks as potential signifiers of cultural impoverishment, to looking at them from a purely natural history point of view, a remarkable fact leaps out at us: the hold that the call of one bird species has had, down the centuries, on the European imagination. After all, there aren't blackbird clocks, are there? Or mistle thrush clocks, or blackcap clocks, or nightingale clocks, all these being birds with charming songs, familiar to many. What European clockmakers long ago latched on to, and have continued with ever since, is the instantly-identifiable two-note call of the cuckoo, because, as I have noted here before, it is the most musical sound in all of nature, being a perfect interval - a descending minor third (in the key of D, which most cuckoos call in, it's A to F sharp). However, if you know the clocks rather than the birds, and actually find them intensely irritating, there's a reason for this: cuckoo-clock makers tend to make the call a major rather than a minor third (ie B flat to F sharp). The resultant interval is much more bouncy and blaring - try it on the piano - compared to the soft and slightly mournful interval you get if you start from a semitone lower, which is what we hear in nature with delight, and what we will be hearing in the British countryside next week. For our cuckoos are nearly back, from their migratory wintering grounds in the Congo and adjacent areas of Central Africa. We know this because we can follow the progress of five cuckoos fitted with satellite transmitters by the British Trust for Ornithology last summer and now returning to Britain. Four are in West Africa, getting ready to cross the Sahara, but Chris, the leading bird, has already crossed the great desert and the Mediterranean, and is now in France - yesterday he was about 70 kilometres west of Chalon-sur-Saone in Burgundy, and he'll probably be back in East Anglia, where he was originally caught, at the weekend. Here comes our springtime, at long last. By my calculations it's running about five weeks late (the big magnolia at the end of my road normally opens about 9 March, and it's still not out). But at least, anyone following the progress of the cuckoos on the BTO's website in these recent freezing weeks could watch them flying from the Congo - Chris began to move north on 4 March - and be reassured that the warm times were indeed on the way towards us. I think of it as a wholly new kind of cuckoo clock. It's far more inspiring than the one which provoked Orson Welles" contempt. This is a clock which sounds, not the hours, but the seasons, and right now it's showing Five Minutes To Spring.