210 A LIST OF THE BIRDS OF PEGU. 
Point, and Mr. Blanford at Bassein. He records it under the 
name of jinlaysoni, which, however, is not found west of the 
Sittang river. The limits of these two birds are very clearly 
and curiously defined by the Sittang. On the same day I 
have shot davisoni on the west bank, and finlaysoni on the 
east, but I have never known either of the birds to be found 
on the contrary sides of the river to these. 
217.—Ixos blanfordi, Jerd. (452 quint.) 
Very abundant in all the plains portion of the province, 
and common as it is at Thyetmyo and Upper Pegu generally, 
it is much commoner in some places in Lower Pegu, such as 
Pegu and Kyeikpadein. 
218.—Iole viridescens, Bly. (452 dec.) 
This Bulbul is spread generally over Lower Pegu, in the 
hilly country chiefly, and extends up the Sittang valley to 
Tounghoo. 
219.—Rubigula flaviventris, Tick. (456.) 
Common throughout Southern Pegu, and extending up to 
Touvghoo both in the hills and plains. 
220.—Brachypodius melanocephalus, Gm. (457 bis.) 
Very common rourd Rangoon and up to Pegu, thence 
extending some miles into the hills. Ihave not met with it 
elsewhere.* 
221.—Brachypodius cinereiventris, Bly. (457 quat.) 
I have no doubt myself that this is a distinct species. I 
have never found any bird with the lower plumage mixed up 
with yellowish green; the grey is always uniform. Mr. 
Hume’s theory (8. F., VI, p. 320) that the skin of cineretventris 
has ceased to secrete the yellow pigment is a very convenient 
one, if you wish to make away with the species.| The same 
* But Blanford got it at Bassein—Ep., S. F. 
+ I have not the least wish to make away with any species. I merely stated the 
fact that the difference between melanocephalus, cinereiventris, and chalcocephalus 
consisted solely in the extent to which the skin did or did not secrete a certain 
yellow pigment. I distinctly said, “ whether these are species or local races,” or what 
not, this is the sole difference between them. Now whether sueh differences consti- 
tute valid species, depends solely on whether they are normal and constant in a 
body of birds over a certain area, or whether they are abnormal or sporadic, 
affecting, like albinism, particular individuals only, and not the bulk of the birds 
of any locality. From what we read, (I do not know the thing of my own 
knowledge) the entire inability to secrete the yellow pigment, which gives us 
chalcocephalus, is a constant and persistent character of a vast number of birds 
covering a huge, but definite area. If this be so. then chalcocephalus must be 
admitted as a good species. But we know nothing of the same kind about the 
partial inability to secrete the yeiluw pigment, which gives us cimereiventris. On the 
