822 Birds of Celebes: Ardeidae. 



The Reef Heron occurs under two forms, one slate-colour, the other white. 

 By some authors these are believed to be two distinct species, by others they 

 are held to be of one species which is dichomatic. Slate-coloured adults and 

 white adults of both sexes are known ; also slate-coloured young and white young. 

 Piebald intermediate examples are often observed ; and slate-coloured and pure 

 white birds are frequently seen paired. In habits the birds are similar, and 

 they live together; but Hume and Davison in the Andaman and Nicobar 

 Islands found that the white bird was (the rule with albinos?) much the shyer 

 and more difficult to shoot of the two. The white form is much less plentiful 

 than the dark, but it seems to occur everywhere with it, even in New Zealand 

 (d IX), where it has been supposed to be absent. The view that there is only 

 one species with strong tendencies to albinism is the more probable one; in 

 the allied species Ardea gidaris of Africa, India and Ceylon, A. coerulea and 

 A. rufa of America closely similar conditions occur, as pointed out by Finsch 

 & Hartlaub, Stejneger, Legge, and Baird, Brewer and Ridgway. Such 

 questions must be stvidied in the haunts of the birds ; from the museum they 

 cannot be answered. 



Another matter which is likely to cause perplexity is the supposed existence 

 of local races. The Reef Heron is known to breed in many localities (Australia, 

 Tasmania, New Zealand, Fiji, Andamans, Arrakan), and it may perhaps be station- 

 ary in some localities ; it is, however, according to Mr. Whitehead (20), a migrant 

 in North Borneo, which means, of course, that it moves in some other spots. The 

 Arrakan and Nicobar birds were separated by Blyth as Demiegretta concolor, but on 

 grounds subsequently shown by Hume to be invalid; more recently Stejneger 

 named those inhabiting the Loochoo Islands and Corean Strait D. ringeri. Without 

 material from all parts it is difficult to form an opinion on this question, to- 

 wards solving which vol. XXVI of the Catalogue of Birds should go far, and 

 in that work Sharpe does not admit D. rwgeri as a species. 



The Reef Heron seems to have its closest affinities with the Indo-African 

 A. gularis (Bosc) in which the white of the throat extends over the submalar 

 region and much farther down the throat, and, as Legge ^points out, it is 

 longer in the leg and has much more of the tibia bare of feathers. The albino- 

 form of D. sacra is likely to be mistaken at first sight for a white Heron of 

 the genus Herodias; it may best be distinguished by its short tarsus, except from 

 H. eulophotes in which, however, the first primary is the longest and the wing 

 is shorter than in sacra. The bill of Demiegretta is peculiar; it is unserrated, 

 stouter than in Herodias, not tapering to a sharp point, but of fairly even width 

 for y^ of its length, the cutting edges meeting at the tip, but not quite meeting 

 for the terminal third behind it — a condition also seen in Anastomus and Esacus 

 magnirostris, for instance, and a result, perhaps, of laying hold of rough objects, 

 such as crabs, coarse-shelled molluscs, etc., on the sea-shore which the birds 

 haunt. The toes of Demiegretta are stout, being covered with unusually thick 

 transverse scales. 



