88 Booth : Migration of the Common Swallow. 
22nd (1913). The bird does not nest in the islands, but is 
plentiful in the first half of May, and numbers were seen 
throughout June, 1913 ! Are these part of the laggards from 
the south, and part of the sterile and non-breeding birds of 
this species ? It is also worthy of note that Swallows should be 
more numerous there in spring than in autumn. Just the 
reverse would be expected if the birds had followed the same 
route on their journey south in the autumn as they had taken 
in their journey north in the spring. 
It will be noticed that those birds nesting near the southern 
limit of the breeding area of this species, have actually arrived 
on their breeding grounds before there is any sign of a movement 
northwards amongst our Swallows in South Africa. It would 
therefore appear as if the Swallows nesting in the neighbour- 
hood of the Mediterranean spend the end of, and beginning 
of, the year further north — that is, in the tropics. 
I believe it was the late Henry Seebohm, a Yorkshireman, 
and a Past -President of the Yorkshire Naturalists’ Union, 
who first propounded the theory that the birds of a migratory 
species which nest at the northern breeding limit of that species, 
are those which migrate to the southern limit of that species 
after nesting is over ; also the birds which nest near the - 
southern breeding area only migrate to the northern area of 
the so-called winter quarters, and those nesting in between 
those areas travel south in proportion. This theory has never 
actually been proved, but it has never been disproved, and much 
evidence has since accumulated towards supporting it. It 
certainly seems as if it were the case with the Swallow. 
In ‘ A Monograph of the Swallows ’ (p. 222), Messrs. 
Sharpe and Wyatt say : — * In Tangiers, Mr. Favier states 
that it breeds, and in autumn numbers of migrants join 
the resident birds, and all depart for their winter home. The 
spring migration takes place in January and February, when 
great flights pass northward.’ In the same work (p. 221), 
Colonel Irby observes : — ‘ About Gibraltar the Swallow 
generally arrives about the 13th of February, although I have 
often seen a straggler in December and January. I have 
seen them crossing the Straits in considerable numbers up to 
the 15th of April; the latest I noticed were passing on the 
24th of that month. I have observed the nest finished on the 
23rd of February.’ In the same work again (p. 221), Mr. 
Howard Saunders writes : — ‘ I was informed that the usual 
date of the appearance of the Swallow at Malaga was the 25th 
of January ; but I did not actually observe it till 4th February, 
1868 (an exceptionally cold year).’ In the same work Dr. 
R. B. Sharpe (pp. 221-2) says : — ‘ Dr. Carvalho has furnished 
me with a table of observations respecting the Swallow as 
observed by him at Coimbra (a little south of Oporto) during 
Naturalist 
