St. John's Lake is a huge tidal inlet on the Cornish
side of the River Tamar, opposite Plymouth. It is an area of saltmarsh
formed when the incoming tide meets the fresh river water. It supports
the greatest number of estuarine birds in Cornwall and attracts the
most species and individual birds in this area. As such it has been
designated under the European Directive on Wild Birds as a Special Protection
Area. Apart from the resident birds it provides an important 'refueling'
stop for birds on migration.