The Eurasian Hobby is a small falcon. It breeds across Europe and Asia and is a long-distance migrant. European birds winter in Africa. More than 5,700 Hobbies have been ringed in 10 European countries, but so far there have been only two ring recoveries south of the Sahara desert. Satellite tracking using the Argos system is now an accepted technique for long distance migration studies of birds. It is generally accepted that any device we burden a bird with should weigh no more than 3% of the bird’s weight if we are not to affect its behaviour.