Apart from really minor variations in plumage, leg-colour and wing-shape, this particular bird so carefully resembles the Chiffchaff that the silent example of beauty can often trigger indecision even amongst expert experts. But when the bird performs all question vanishes, with regard to the willow warbler has a really definite agreement of enjoyable notes that constitute a genuine song. This normally occurs about a week after the Chiffchaff, to ensure that any leaf-warbler observed in March is much more likely to be the second option.