The earth, the water, and the air, throughout their broad domains, must each of them be provided with inhabitants peculiarly constructed to live in their diversified regions. Upon the earth, we find the level ground, the mountain, and the glen; we find the pathless forests, and the solitary trees and shrubs, and bushy underwood. We cast our eyes upon the waters, and we see the world of ocean covering two-third parts of this great globe, stretching from pole to pole, rolling its mighty waves through every zone; we see the creeks and shallow bays that margin it all round, and watch the waves as they approach the shore and lay them down to sleep upon the beach. There are the rivers, too, and lakes, and swamps and marshes which are neither land nor water, sometimes overspread with floating vegetation, sometimes a broad expanse of ooze and rushes far too soft to bear the weight of creatures that might try to walk upon the treacherous surface. We look into the air, and there we find between the earth and sky abundant room for birds of every wing. If, therefore, with this little map of the world before us, we reply to the question propounded above, we should be tempted to say that there must necessarily be as many different types of organisation as there are districts therein enumerated; and doubtless a reference to any system of ornithology, however much the classification may be confused by preconceived theories, will convince us that such is essentially the foundation of any natural arrangement. In taking, therefore, a brief survey of the principal groups, or ORDERS, under which the feathered races have been distributed, we will begin with those appointed to live on trees, inasmuch as these are regarded by the author of the following pages as being entitled to the highest rank in the class to which they belong, rivalling in intelligence, as some of them do, the apes and monkeys of which they are in general the inseparable companions.