HYDROCHELIDON LEUCOPTERA. 211 
and, keeping to the sea-coast, is the latest to aiTive of all the 
family. They are nowhere very abundant ; but a few nest 
near the mouth of the Guadiarro about the end of May, as 
well as in other localities on the coast. 
The earliest date on which I noticed one was on the 10th 
of May ; and the latest was on the 25th of October. 
The small size of this species will distinguish it ; the bill is 
yellow. 
Total length about 8*5 inches. 
304. Hydrochelidon hybrida (Natt.). The Whiskered 
Tern. 
" This Tern is scarce near Tangier, and seen only on pas- 
sage during April, returning south in August. Immense 
numbers are found breeding at the lakes of Ras Dowra, where, 
nesting together in vast colonies, they bear the local name of 
Mershik." — Favier. 
On the Spanish side the Whiskered Tern arrives about the 
middle of April, and is seen near Gibraltar only on migration. 
Hovering over every swamp and wet spot, they soon pass on to 
their breeding-haunts in the marismas,where, among the rushes 
and sedges, they nest about the middle of May in colonies. 
Like other Terns, they lay three eggs of a pale green colour, 
spotted with blackish brown ; but these eggs vary a great deal. 
I saw a large flock of these Terns on the sea near Cadiz on 
the 18th of July. 
In the adult birds the underparts are of a very dark grey, 
in some almost black. 
The bill is darker in colour than the legs,which are vermilion. 
The total length is about 11 '5 inches. 
305. Hydrochelidon leucoptera (Meisn.). The White- 
winged Black Tern. 
The only instance I know of the occurrence of this bird is 
a single specimen shot in May 1869 at Sharf el Akab, near 
Tangier. It is not included in Favier's list; and I never 
myself met with any on either side of the Straits : probably 
it rarely wanders so far west. I have several times imagined 
that I saw it, but upon shooting the birds found them to be fine 
p 2 
