174 
BIRD-LIFE. 
a considerable flock, much to the annoyance of the 
farmers, whose corn they devoured. 
On the other side, many birds disappear from certain 
districts without apparently any reason. The neighbour¬ 
hood presents the same appearance after their departure, 
as it had during the time they used to be found there, 
and yet not a single pair remains in the abandoned 
region. While speaking of this phenomenon, it may 
be easily understood, from the circumstances attending 
the fact, that man can banish certain birds from his 
neighbourhood by destroying or disturbing their breeding- 
places : this, of course, bears no reference to the emigra¬ 
tion of birds of their own free will. It is an undoubted 
fact that the Ibis was common in Egypt thousands of 
years ago. Many thousands of Ibis-mummies were 
deposited in the pyramid of Sakahra, which was erected 
in their honour: yet in these days such a thing as an 
Ibis is not to be found there, they have all withdrawn to 
the Soudan or the Nile; for what reason no one knows. 
In the neighbourhood of my birth-place, black and gray 
Woodpeckers, Eavens, Magpies, Hoopoes, Whinchats, &c., 
all disappeared, although they could, even at the present 
day, sustain life there. From this we may gather that 
the zone of distribution of certain species is in no wise 
the same at all times. 
On sea and ocean these conditions assume another 
character ; here distance vanishes, and with it, more or 
less, the causes which bind birds to a locality; the ever- 
moving water itself naturally extends distribution, and 
this explains, in a great measure, why we find, upon all 
the oceans of the globe, the same species of aquatic 
birds, or, at all events, very closely allied forms. In 
general, one may state that the zone of distribution of 
