PREFACE.
Circumstances have retarded the completion of the present volume, chief among which were interruption by field work (including a second visit to Costa Rica), occasional periods of illness, and the specially difficult character of some of the included groups; furthermore, one large family (the Woodpeckers, Picidæ) was worked up and even set in type, but was finally omitted because its inclusion would increase the bulk of the volume far beyond a convenient size. It will, therefore, be included in Part VI.
The Families included in this and preceding volumes are as follows:
Part I, issued October 24, 1901, included the Family Fringillidæ (Finches) alone.
Part II, issued October 16, 1902, included the Families Tanagridæ (Tanagers), Icteridæ (Troupials), Coerebidæ (Honey Creepers), and Mniotiltidæ (Wood Warblers).
Part III, published December 31, 1904, included the Motacillidæ (Wagtails and Pipits), Hirundinidæ (Swallows), Ampelidæ (Wax-wings), Ptilogonatidæ (Silky Flycatchers), Dulidæ (Palm Chats), Vireonidæ (Vireos), Laniidæ (Shrikes), Corvidæ (Crows and Jays), Paridæ (Titmice), Sittidæ (Nuthatches), Certhiidæ (Creepers), Troglodytidæ (Wrens), Cinclidæ (Dippers), Chamæidæ (Wren-Tits), and Sylviidæ (Warblers).
Part IV, issued July 1, 1907, contained the remaining groups of Oscines, namely, the Families Turdidæ (Thrushes), Zeledoniidæ (Wren-Thrushes), Mimidæ (Mockingbirds), Sturnidæ (Starlings), Ploceidæ (Weaver Birds), and Alaudidæ (Larks), together with the Haploophonæ or Oligomyodian Mesomyodi, comprising the Families Oxyruncidæ (Sharp-bills), Tyrannidæ (Tyrant Flycatchers), Pipridæ (Manakins), and Cotingidæ (Chatterers).
The present volume contains the Tracheophone Mesomyodi, represented by the Families Pteroptochidæ (Tapaculos), Formicariidæ (Antbirds), Furnariidæ (Ovenbirds), and Dendrocolaptidæ (Wood-hewers), together with the Macrochires, containing the Families Trochilidæ (Humming Birds) and Micropodidæ (Swifts), and the Heterodactylæ, represented only by the Family Trogonidæ (Trogons).
The number of species and subspecies described in the five volumes is 2,038, with 351 additional extralimital forms characterized in the "keys." About 1,150 to 1,200 forms remain to be treated in subsequent parts of the work.
Acknowledgments for the loan of specimens for use in the preparation of the present volume are due to the same individuals and public
