September 1952 – vol. 45, issue 9–316 IN 1950 and again in 1951 the British Bird Observatories have exchanged information about the occurrences of selected species of birds. A study of this collated information appears to throw some light on the pattern of migration to and through the British Isles in spring. The simple conception of this pattern of spring migration is one of a south to north movement. The birds, it is assumed, enter ... This article is only available to registered users.To read more, please log in or purchase a subscription.