Observer could see no reasons such as mating or selection of mates going on, or driving away of last year's young and so on to account for the periodical movements. In fact no reason for the movements could be arrived at and the only conclusion was that such periodical movements were fairly regular and arose from some unknown cause. SUMMARY OF TIDE LIKE MOVEMENTS OF BIRDS Beyond establishing the fact that tide like movements of birds did take place on Uvea at regular and irregular intervals in many species present on the island, the shortness of my stay pre- vented me going more deeply into the causes of this movement, and no real proofs were obtained, but observers believe the causes are probably due to two factors. 1. Overpopulation of bird life on the island (and en- roachment of natural habitat by cultivation to a limited extent). This seemed to be pointed to by the fact that the commonest species showed the movement most clearly. This has caused a tendency for strictly regular habitat species to try and adapt themselves to unusual habitat and possibly partially succeeding. Uvea being a rather infertile island shows a definite lack in most fruit eating species, a good supply of fruit and insect eaters, and a good supply of flower, nectar-insect eaters and a fair percentage of purely insectivorous birds. The latter probably having arrived at a later date than the other. Pachycephala being a mollusc eater and also possibly the earliest arrival has increased even more rapidly, Myiagra possibly arrived somewhat later and is not yet as well established as the other species (Pacy. and Gerygone). Rhipidura has only just arrived and is not yet established and still exceedingly rare. Aplonis a fruit-snail and insect eater has progressed better than the purely fruit eating pigeons.