PELAGIC BIRD FAUNAS OF THE INDO-PACIFIC OCEANS 471 



Pacific. I.S. fuscata and S. anaetheta are sympatric and S. anaetheta and 

 S. lunata are probably allopatric; the records of their breeding together 

 should be re-examined. 



Anous spp. 



The Noddy Terns (Anous stolidus) have a closely similar geo- 

 graphical pattern to the Sterna fuscata-anaetheta group just discussed. 



The species group, minutus-tenuirostris, are now widely separated, 

 one (minutus) extensively distributed in the Pacific and Atlantic, the 

 other (tenuirostris) confined to two breeding centres in the Indian 

 Ocean. Recent reviewers have tended to consider them as races of one 

 species, but the plumage differences are rather distinct, and it would, 

 perhaps, be better to rank them as having attained specific differentia- 

 tion, although considering them as semi-species for purposes of zoo- 

 geographical discussion. 



Gygis alba 

 Widely distributed in the tropics of the three oceans. It is absent, 

 however, from the Indo-Malayan and northern Australian area, the 

 two nearest breeding colonies being at North Keeling in the Indian 

 Ocean and Palau Island in the Pacific. 



Procelsterna spp. 

 The Grey Noddies, P. cerulea and P. cinerea, occur only in the 

 tropical Pacific, where the two species have an allopatric breeding dis- 

 tribution, P. cinerea being the more southern form. 



Sterna sumatrana 



An Indo-Pacific form, but in the latter ocean restricted to the west- 

 central group of islands. It is found in the Malayan region, but has 

 not been reported in northern Australia, west of Torres Strait, or in the 

 Timor and Banda seas. 



Sterna bergii and S. hengalensis 



These two related terns appear to be dominant in the Indian 

 Ocean region. S. bergii has the more extensive distribution, and has 

 spread into the cooler waters of southern Africa and southern Australia. 

 It has colonised the central southern Pacific, as a breeding species, east 

 to the Marquesas, but has not crossed the Equator to the north or gone 

 south beyond the Kermadecs. 



S. bengalensis has barely entered the western Pacific by occupying 

 the northern part of the Great Barrier Reefs, in Queensland. 



Neither species has reached the Atlantic. 



