THE arrival of the Internet has provided a huge boom in information about one of nature's greatest events - the worldwide migration of millions of birds - and British bird-lovers are being invited to become migrant detectives.

The British Trust for Ornithology was one of the first internationally-recognised scientific bodies to enlist the help of enthusiastic amateur bird-watchers with access to the Internet to report sightings of migrant species like swallows and cuckoos, which has helped the trust build a huge data base on visiting species.

This has now become an international movement and this weekend, May 12/13, the second ever World Migratory Bird Day is being held across the globe, organised by the African Eurasian Waterbirds Agreement and the Convention on Migratory Species.

The BTO is organising the British effort and is inviting anyone with an interest in birds to take part. See www.worldmigratorybirdday.org and www.birdtrack.net