Cyclones are outside of control but would not be such a serious factor if the above protections were granted the species. COLLOCALIA SPODIOPYGIA LEUCOPYGIA (WALLACE):- This is the commonest species of Collocalia on Uvea and I couldn't understand any previous observer overlooking it, but later observations drew my attention to a peculiarity about the species which seemed definitely to point to a fact I had previously suspected. This was that this species shows a slight north and south movement each year. E.g., roughly birds from southern N.H. move south to the Loyalties. Loyalty birds move south to N.C. all moving back for the breeding season. Actually the movement may only be from one island to another, perhaps 60 miles or so and may not necessarily be N. and S., but I believe that the birds definitely move away and back to breeding colonies. Tanna Island in the N.H. where they are rare except in the north, where coraline cliffs form suitable breeding colonies for a small population, re- ceives a big influx from Erromanga or elsewhere, making the bird common where they were almost or actually entirely absent before. Similar conditions occur in other parts of the group. In and about breeding islands the species is always common, but on shooting it will be seen 90 per cent or more of birds are immatures, yet this species only lays one egg and has a definite breeding season. Actually I do not think the skull of this species completely ossifies till the end of the second year, but a large area of it does and even allowing for this the preponderance of immatures is not accounted for. Sex ratio seems to be about normal with a slight preponderance of ♂ except at breeding time when ♀ seem