April is an exciting month for birds, with summer migrants arriving and winter visitors slipping away. But what do we really know about the incredible journeys 'our' migrants make? DOMINIC COUZENS takes a bird's - eye view of one of the greatest natural wonders. In britain, we rejoice at seeing the first swallow of spring. It puts the seal on the season and symbolises newness and vigour. Similarly, when we spot our first house martin or hear our first chiffchaff, we can almost feel the sun on our backs.