NOTES
ON
MR.
WILLIAMSON'S
LECTURE
by W . H . PAYN.
THE SPEAKER dealt chiefly with various types of irruptive and eruptive migration when, following it is presumed an unusually successful breeding season, the excess population of what are normally fairly sedentary species, show very abnormal movements sometimes on a considerable scale. In Britain, for instance, the hedge sparrow is now known to make considerable eruptive movements at times, as also do blue and great tits. The lecturer also described the massive westward movement of the common crossbill that took place during the summer of this year. Birds from eastern Europe occurred throughout western Europe. In Britain they first appeared in the south, with the majority gradually working up the west coast of Britain as far as the Western Isles and even St. Kilda. Another movement consisting largely of parrot crossbills from Finland and Scandinavia also reached the north-east coast. During this latter movement at least a hundred thousand woodpeckers are said to have occurred on the Aaland Islands in the Baltic. Other pine-forest species such as waxwings and rough legged buzzards are thought to be irrupting. The lecturer also described abnormal westward movements of such rare species as the melodious warbler which breeds in central Europe and the Iberian peninsula and has recently occurred in small numbers in Britain, Raddes warbler from Turkestan and— a very topical note for Suffolk naturalists—the past eruptions of the houbara bustard. Other species whose movements were illustrated with the aid of weather charts were the blackbird, song thrush, goldfinch and linnet as well as the Iceland races of the redwing and merlin. Mr. Williamson finished by showing some very fine coloured slides of Fair Isle, the Isle of May and some of the West Coast bird observatories.