104 HIRUNDINID^. 
slightly larger in size, I think they are the male birds ; 
but I would not, even for the sake of proving this, kill 
one. I remember, on a very cold day (the 13th of March, 
1874), Mr. Stark particularly drawing my attention to this 
difference in the pairs of birds, which, driven by the cold into 
the stables and outhouses of the venta at Pulverilla, were 
sitting side by side, touching one another, allowing us almost 
to catch them. The contrast in their colour was then most 
conspicuous ; but they appear gradually to lose this rufous 
tinge as the season advances, and by the end of April it 
is not apparent. 
125. CoTYLE RiPARiA (Linn.). The Sand-Martin. 
" Migratory, and the least abundant of the Swallows 
about Tangier, arriving to cross the Straits in March and 
April, returning in October to disappear for the winter." — 
Favier. 
I found the Sand-Martin at Ras-Doura in small numbers, 
and have no doubt that they were nesting in the vicinity ; 
they nest in the neighbourhood of Seville, but near Gibraltar 
are only met with on passage. The first seen by me was on 
the 24th of March 1870, 22nd of March 1871, 24th of 
February 1872, 28th of February 1874; they were seen 
passing as late as the 24th of April. On the 13th of May I 
saw, in the evening, over some marshes near Vejer, a flight 
of Sand-Martins numbering many hundreds ; I might say, 
thousands. I noticed them on the 14th of October on their 
southward journey. 
126. CoTYLE RUPESTRis (Scop.) . The Rock-Martin. 
" Nearly as common as the House-Martin about Tangier. 
Sometimes they pass in large flights, crossing the Straits in 
February and March, returning in October and November.^' 
— Favier. 
The Rock- or Crag-Martin, though universally distributed 
during the breeding-season in the rocky sierras, is to a great 
extent migratory. Those which do not quit the country 
appear during the day-time in low ground near the coast about 
