XU 
INTRODUCTION. 
is not confined to genera only, but may be traced, more or less, 
in most of the families, and is very remarkable throughout the 
Scolopacidse, the eggs of which are much pointed at the smaller 
end, and almost invariably four in number. 
There is too, in many genera, a beautiful analogical resem¬ 
blance with others nearly allied to them. The Eagles and 
Hawk tribe (nearly all of which breed aloft) approach by the 
genus Circus, which breeds upon the ground and lays eggs 
which are white or nearly so, that section of the Owls which 
is the most Hawk-like, the species of which also, departing 
from the habits of the rest of their family, breed,upon the 
ground. The eggs of the following genera, Corvus, Fregilus, 
Pica, and Garrulus, are all closely allied, as are those of the 
Poller, Merops, and Alcedo. 
Eggs are subject to much variety, and are not without those 
apparent discrepancies which beset the study of other branches 
of Natural History, and which are only to be reconciled by 
oft-repeated observation, and by combining with their study a 
knowledge of the nests in which they are found. And thus, as 
regards the different species of a genus : although the eggs of 
some of the Thrushes usually bear but slight resemblance to 
each other in colour, we shall find upon a closer acquaintance 
with them, that there are other connecting links. The nests of 
all the species are much alike, each being strongly cemented 
with clay; and much as the eggs of the Common Thrush and 
the Blackbird appear to differ at first sight, they nevertheless 
run imperceptibly into each other, in some of their varieties. T 
have seen eggs of both species, of a clear spotless blue. My 
friend, Mr. Henry Doubleday, one year found several nests of 
the Blackbird, at Epping, in one locality, the eggs of which 
were all of this description ; a variety perpetuated, probably, 
through the several individuals of the same family. Eggs of 
the Wheatear are occasionally spotted like those of the allied 
species, and eggs of the Spotted Flycatcher, as well as those of 
the Pied, are sometimes of a uniform unspotted blue. No one 
who has seen the nests of the Swallow and the House Martin 
