144 REV. W. SERLE ON 
weather, birds naturally returned home. In these opinions 
there might be a large amount of truth, but time was to be 
the revealer, and I need not say biological research into the 
primary forms of the various families of birds is to lead us 
far along the road to the determination of the truth. In 
this ebb and flow of bird-life, as far as the Old World is 
concerned, there naturally arises the question—Supposing 
the north to be the ancestral home, what accounts for the 
varying distances to which birds travel in winter? Why 
should the blue-throats and willow-warblers of the Norwegian 
northernmost regions, or the myriad armies of waders of the 
Siberian tundras, travel to the very south of Africa or further, 
and other birds should go no further than the basin of 
the Mediterranean ? And if our northern birds penetrate 
so numerously into the southern hemisphere in winter, why 
do so few southern birds, or, rather, why do practically none 
of them, spend their winter with us? Observe, in reply, 
that hard-billed birds are better fitted for the struggle of 
existence, and winter would not therefore drive them so far 
south; also, as they feed largely on seeds during winter, or 
even during all the year, the land area as they are driven 
south suffers no contraction, and naturally, therefore, from 
their most northern nesting homes to their most southern 
winter quarters there is a continuous connection; they 
therefore do not migrate so far. It is a very different 
matter with the class of wading birds. Their nesting quarters 
in the desolate regions of Siberia and North America are 
unlimited—the whole vast extent is bog and lake and 
sea-shore; birds are hatched and reared by the millions. 
When winter forces this vast army south, it forces them 
into regions where food is not so abundant ; the vast tracts 
that are under forest or cultivation are destitute of food. 
Notice also there is less land south of the Equator than 
to the north, and you will easily see why these Arctic birds 
are many of them cosmopolitan. Seebohm accounted for 
the lengthy migration of these birds by the fact that, being 
accustomed to long light in Arctic regions, they naturally, 
when they did migrate, went as far as they could. The distri- 
‘ution of land is in all likelihood the reason. Many of these 
birds remain with us—for example, turnstones and ringed 
