Tortoises with Zips
David Craig: The Snow Geese by William Fiennes, 4 April 2002
“... caged garden warblers hop south-west while their free fellows are flying south-west across France and Spain, then hop south and south-east just when the free birds turn south and east over Gibraltar. Further caging and experimenting has shown how birds navigate by the stars. I’m glad to know these things, and glad that Fiennes relates them so ... ”