The Birds of India. 
65 
more like one another owin^ to the wearing away of the outer edges of 
their feathers ; hut it is always possihle to distinguish hetweeu them at a 
glance. The two species meet at ahout the latitude of Bonihay. Oates 
states that in a certain zone, from Ahniednagar to the month of the Goda- 
veri vallev, both species occur, and they do not appear to interbreed. 
It seems impossible to maintain that natural selection, acting 011 
minute variations, has brought about the divergence between these two 
species. Kveii if it be asserted that the difference in the colour of the 
feathers of the back of tlie two cocks is in some way correlated with 
adaptability to their particular environment, how are we to explain the 
fact that in a certain zone both species flourish 
Bur.BULS. 
A similar phenomenon is furnished by the Red-vented Bulbuls. This 
genus falls into several species, each corresponding to a definite locality 
and differing only in details from the allied species, as, for example, the 
distance down the neck to which the black of the head extends. There is 
a Punjab Red-vented Bulbul (iMolpasles inlennediiis), a Rengal (Molpasles 
bengalensis), a Burmese {Molpastes burinanicns), and a 3Iadras {Mo/pasies 
h<^inorrhous) species. 
It does not seem possible to maintain the contention that these 
various species are the products of natural selection, for that would mean if 
the black of the head of the Punjab species extended further into the neck 
the bird could not live in that part of the country. As there seems to be 
some intercrossing between these so-called species at places, such as Luck- 
now, where they meet, I am inclined to regard them as local races of a 
species, rather than as species of a genus. This, however, does not affect 
the difficulty which they present to Wallace and his school. 
It is templing to believe that these slight external differences are in 
some way or other produced by the direct action of the climate to which 
the various forms are subjected. Unfortunately for this hypothesis, there 
is evidence which seems to disprove it. For example, the common house- 
sparrow in India differs from our P^nglish sparrows in having white cheeks, 
l)ut those Indian sparrows which are brought to thiscountr}' do not lose the 
white cheek patch as they should do had it been the result of the direct 
action of the climate in India. 
Thk Rkd Turtle Dove. 
The Red Turtle Dove {Oenopopelia tranquebarica) is another Indian 
bird of great interest to the biologist. It is widely distributed over the 
plains, and undergoes local migration. lis nesting and feeding habits are 
identical with those of the other doves common in India— the Ring, the 
Spoited. and the little Brown Dove. But, while in these species the cocks 
and the hens are alike in external appearance, the Red Turtle Dove displays 
considerable sexual dimorphism. So great is the difference between the 
