Conservation groups are warning that the stricken oil tanker currently being escorted away from Spanish waters is putting some of the country's most vulnerable birdlife at risk. The oil tanker Prestige has left behind a 32-kilometre-long slick, which is believed to be just offshore. The tanker was on its way from Latvia to Gibraltar last night when it encountered violent storms about 48 km off the province of Galicia in north western Spain. Of particular concern to conservationists are the many species of migratory birds that use the area as a resting stop before continuing south.