My brother sent me a link to this review of Secret Pigeon Service in the London Review of Books. It really seems to function as a (pretty lengthy, and interesting) summary. LRB · Jon Day · Operation Columba: Pigeon Intelligence
And in North Africa ;-) THE BRITISH ARMY IN NORTH AFRICA AND THE MIDDLE EAST 1940-1947 E18627 : Object description - Original wartime caption: South Africans fixing a message to the leg of a pigeon before releasing it to fly back to Corps H.Q. Taken by Sergeant Travis. Catalogued 28d10m1942. THE BRITISH ARMY IN NORTH AFRICA AND THE MIDDLE EAST 1940-1947 E18628 : Object description - Original wartime caption: The pigeon is released. In a few minutes it will have reached its loft and the message will be at Corps H.W.