INTRODUCTION.
The present volume is the first of the series of the new edition of the 'Avifauna of British India,' and, funds permitting, it is proposed to bring out about one volume every two years until the work is completed.
It has been my endeavour in writing this volume to disturb as little as possible the classification adopted by Oates in the first edition but during the thirty-two years that have elapsed since his first volume was published, much scientific work has been done and many discoveries made which have rendered alterations imperative; some of these, unfortunately, are of a drastic nature.
In the first place, the trinomial system has been adopted — a decision which has added very greatly to the number of birds to be described, i.e. to the total number of species and subspecies, though, on the other hand, it has reduced the number of species, for it has relegated to their proper positions as subspecies or geographical races many forms which have hitherto improperly held the status of species.
In using the trinomial system I have adhered to the following rules : —
Forms, or groups of forms, have been named as specific when there are no forms known which directly connect them with other forms or groups of forms.
Subspecies or geographical forms have been recognized when they differ in degree either in size, colour or some other characteristic from the forms with which they are most closely connected, yet, though linked with these forms by others which are intermediate, are themselves constant within some given area.
