MIGRATION OF BIRDS. 289 
converse of the conditions obtaining in the far north of Asia. 
From about October to April, at a time when Siberia is frozen 
out, there are vast areas all over the ‘‘ dry zone ”’ of the Island 
which are swamped by the heavy monsoon rains, and afford 
abundant sustenance for the hordes of Waders and aquatic 
birds which visit us. From April to October these mud flats 
and paddy fields are parched and dry, and many of the tanks 
have shrunk to mere puddles. The aquatic and semi-aquatic 
migrants would have a meagre time if they all stayed on. 
Frem what regions do our migrants arrive ? The Passerine 
migrants, which are most strongly represented by the Warblers, 
Shrikes, Flycatchers, Thrushes, and Wagtails, mostly come 
from North India. The same may be said of the Cuckoos. 
Most of the migrant Hawks and Waders come from further 
afield, from temperate or Northern Asia. 
I have noted earlier that the Himalayas in a great 
measure form the dividing line between the winter and 
summer quarters of the Asiatic migrants, just as the Sahara 
does for those of Europe and Africa. There is this difference 
though: on the southern slopes of the Himalayas we have 
an extensive regional belt of elevated land with temperate 
conditions of climate, and many birds find a congenial 
breeding ground there without continuing their course 
further north. It is no wonder, therefore, that many of 
the more delicately formed Passerine migrants settle down 
to breed in large numbers in Cashmere and other Himalayan 
districts, which are well suited for them, while the stronger- 
winged Harriers, Falcons, and Waders carry on to the 
enormous breeding grounds in the marshes of Siberia. 
This distinction, however, is by no means universal. Some 
Swallows and other Passerine species breed on the north as 
well as on the south side of the great ranges. The Forest 
Wagtail—Limonidromus indicus—retreats to Northern China 
and Eastern Siberia, and so on, while some of the Kestrels and 
Woodcocks breed on the Himalayas. 
It is quite possible, though in the present state of our 
knowledge it would be unwise to be dogmatic, that the axiom 
that those birds which breed furthest north winter furthest 
south holds good to a certain extent, in which case our Ceylon 
