FRYER— FORMATION OF ALDABRA, ETC. 417 



Two insectivorous bats were noted ; one, Taphozous mauritianvs, was seen but was 

 scarce, while a second, Tricsnops furcula, Trouessart, was not uncommon on Picard near 

 the settlement. A specimen of the latter species was sent to M. Trouessart, who has 

 kindly compared it with his type and confirms my identification. 



Of introduced mammals there are rats (Mus rattus), mice (Mus musculus), cats and 

 goats. Of these the rats alone deserve further mention, for they have spread over the 

 whole atoll, extending even to the small lagoon islands where they catch and eat the land 

 crabs (Cardiosoma, etc.) for want of other food. These must form serious antagonists to 

 the land birds, and perhaps to the giant tortoise also, as they are reputed to eat its eggs. 

 The cats*, which only exist at Takamaka, are, I think, decreasing, and consequently 

 cannot be expected to keep down the rats, which will probably continue to increase until 

 want of food sets a definite limit to their numbers. 



(6) Aves. The resident land birds have been described by Kidgeway f. They are 

 of interest in being almost all peculiar to the atoll. It is however noticeable that all are 

 very closely related to Malagasy forms and doubtless their origin is thus indicated. Full 

 descriptions need not be given here, but a few notes as to their natural history, which does 

 not seem to be anywhere recorded, may be of interest. 



Most conspicuous and typical of the atoll is undoubtedly the ibis (Ibis abbotti), which 

 resembles the sacred ibis and is closely related to Ibis bernieri of Madagascar. It formerly 

 was abundant, but now is absent from Picard Island and uncommon over the north of the 

 atoll, though it is still fairly distributed along Main Island, in the east of which it is, 

 indeed, common. In habit it is a shore bh-d, feeding along the edge of the lagoon in the 

 mangrove swamp when the tide is low, and at high tide flighting inland, where it is to be 

 found round the freshwater springs of Takamaka and the brackish pools which abound 

 everywhere. Its food consists of small crabs and other marine creatures, but a few birds 

 were always to be found picking through the rubbish from Michel Island camp and 

 generally playing the part of scavengers. Night is spent roosting on a tree, the large 

 Calopliyllum trees round the wells being especially haunted. Its cry is a harsh wheeze. 

 In flight the ibis is heavy and laboured, though its broad wings allow it to soar so 

 that it occasionally circles round for some time on outstretched pinions when it is 

 choosing a site on which to perch. In character it is tame and inquisitive, while owing 

 to its peculiar form, colouration and a habit of continually twisting its head about, it has 

 always a rather ludicrous appearance, and this is especially the case when it is draggled or 

 soaked with rain. 



The ibis nest in colonies in the trees, choosing especially those in the depths of the 

 mangrove forests. Only one nesting tree was found tenanted. It was a small Cenops, 

 the top of which had been so trampled down as to be flat. The nests, seventeen in all, 

 were composed of a few sticks and resembled those of the gannet (Suln leucognster). Two 

 chalky-shelled eggs of a greyish-white colour were the maximum found in one nest. 

 If the following habit is general but a small percentage can reach maturity. Before the 

 birds have commenced incubation, they leave en masse when the tide is low to feed, but 



* If numerous they would completely kill out the rails and possibly other endemic species. 

 t Proceedings of the U.S. National Museum, Vol. xvi., p. 597. 



