14 
So little has as yet been ascertained respecting the climatology 
of western, north-western and northern Australia, that it is not 
known whether they also are subject to these tremendous visita- 
tions ; but as we have reason to believe that the intertropical parts 
of the country are favoured with a more constant supply of rain as 
well as a lower degree of temperature, it is most probable that they 
do not there occur. 
Independently of the vast accession of birds attracted by the 
great supply of food, as mentioned above, there are many species 
which make regular migrations, visiting the southern parts of the 
continent and Van Diemen’s Land during the months of summer, 
for the purpose of breeding and rearing their progeny, and which 
retire again northwards on the approach of winter, following in 
fact the same law which governs the migrations of the species in- 
habiting similar latitudes of the Old World. There are also 
periods when some species of birds appear to entirely forsake the 
part of the country in which they have been accustomed to dwell, 
and to betake themselves to some distant locality, where they re- 
main for five or ten years, or even for a longer period, and whence 
they as suddenly disappear as they had arrived. Some remarkable 
instances of this kind came under my own observation ; for in- 
stance, the beautiful little warbling Grass Parrakeet ( Melopsittacus 
undulatus), which, prior to 1838, was so rare in the southern parts 
of Australia that only a single example had been sent to Europe, 
arrived in that year in such countless multitudes on the Liverpool 
plains, that I could have procured any number of specimens, and 
more than once their delicate bodies formed an excellent article of 
food for myself and party. The Nymphicus Novce Hollandice forms 
another case in point, and the beautiful Harlequin Bronze-winged 
Pigeon ( Peristera histrionica ) a third ; this latter bird occurred in 
such numbers on the plains near the Namoi in 1839, that eight fell 
to a single discharge of my gun ; both the settlers and natives assured 
me that they had suddenly arrived, and that they had never before 
been seen in that part of the country. The aborigines who were 
with me, and of whom I must speak in the highest praise, from the 
readiness with which they rendered me their assistance, affirmed, 
upon learning the nature of my pursuits, that they had come to 
meet me. The Tribonyx ventralis may be cited as another species 
whose movements are influenced by the same law. This bird 
visited the colony of Swan River in 1 833, and that of South Australia 
in 1840, in such countless myriads, that whole fields of corn were 
trodden down and destroyed in a single night; and even the streets 
and gardens of Adelaide were, according to Captain Sturt, alive 
with them. 
If we compare the ornithology of Australia with that of any other 
country in similar latitudes and of the same extent, we shall find 
that it fully equals, if it does not exceed them all, in the number of 
species it comprises; and the parts of the country still unexplored 
doubtless contain many yet to be added to the list of its Fauna. 
In the course of the present work it will be found that I have 
frequently given a wide range of habitat to some of the species, and 
