NATURAL HISTORY OF SELBORNE, 103 
Db) mR. ato. 
TO THE SAME. 
SELBORNE, Seft. 22d, 1774. 
DEAR Str,—Before your letter arrived, and of my own accord, 
I had been remarking and comparing the tails of the male and 
female swallow, and this ere any young broods appeared ; so that 
there was no danger of confounding the dams with their fz//z- 
and besides, as they were then always in pairs, and busied in the 
employ of nidification, there could be no room for mistaking the 
sexes, nor the individuals of different chimneys the one for the 
other. From all my observations, it constantly appeared that each 
sex has the long feathers in its tail that give it that forked shape ; 
with this difference, that they are longer in the tail of the male 
than in that of the female. 
Nightingales, when their young first come abroad, and are 
helpless, make a plaintive and a jarring noise ; and also a snapping 
or cracking, pursuing people along the hedges as they walk: these 
last sounds seem intended for menace and defiance. 
The grasshopper-lark chirps all night in the height of summer.* 
Swans turn white the second year, and breed the third. 
Weasels prey on moles, as appears by their being sometimes 
caught in mole-traps. 
Sparrow-hawks sometimes breed in old crows’ nests, and the 
kestril in churches and ruins.t i 
There are supposed to be two sorts of eels in the island of Ely. 
The threads sometimes discovered in eels are perhaps their young: 
the generation of eels is very dark and mysterious. } 
Hen-harriers breed on the ground, and seem never to settle on 
trees. 
* Salicaria locustella, see Letter XVI. 
+ We have known a kestril breed in the deserted nest of a magpie. 
t Three species of British eels have now been clearly made out. Two very distinct by 
the form of the head, in the one narrow, in the-other broad, and consequently have been 
named sharp and broad-nosed eels. The third is of intermediate form, and called the 
snig. Ely was famous for its eels, and is said to have derived its name from the circum- 
stance of its rents being formerly paid in eels. The ‘‘threads’’ would be intestinal 
worms, perhaps Fz/a77@.-—Eels are oviparous and generate like most other fishes, having 
bony skeletons. 
