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 iulness, and the specially 
difficult character of some of the included groups; furthermore, one 
large family (the Woodpeckers, Picidse) 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 wil, there- 
fore, 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 Fringillide 
(Finches) alone. 
Part II, issued October 16, 1902, included the Families Tanagrids 
(Tanagers), Icteridee (Troupials), Coerebidee (Honey Creepers), and 
Mniotiltidszs (Wood Warblers). 
Part III, published December 31, 1904, included the Motacillide 
(Wagtails and Pipits), Hirundinide (Swallows), Ampelide (Wax- 
wings), Ptilogonatide (Silky Flycatchers), Dulide (Palm Chats), 
Vireonide (Vireos), Laniide (Shrikes), Corvide (Crows and Jays), 
Paride (Titmice), Sittide (Nuthatches), Certhiide (Creepers), Trog- 
lodytide (Wrens), Cinclidee (Dippers), Chamezidz (Wren-Tits), and 
Sylviide (Warblers). 
Part IV, issued July 1, 1907, contained the remaining groups of 
Oscines, namely, the Families Turdide (Thrushes), Zeledoniide 
(Wren-Thrushes), Mimide (Mockingbirds), Sturnide (Starlings), 
Ploceide (Weaver Birds), and Alaudide (Larks), together with the 
Haploophone or Oligomyodian Mesomyodi, comprising the Families 
Oxyruncide (Sharp-bills), Tyrannide (Tyrant Flycatchers), Pipride 
(Manakins), and Cotingide (Chatterers). 
The present volume contains the Tracheophone Mesomyodi, repre- 
sented by the Families Pteroptochide (Tapaculos), Formicariide 
(Antbirds), Furnariide (Ovenbirds), and Dendrocolaptide (Wood- 
hewers), together with the Macrochires, containing the Families 
Trochilide (Humming Birds) and Micropodide (Swifts), and the 
Heterodactyle, represented only by the Family Trogonide (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 subse- 
quent parts of the work. 
Acknowledgments for the loan of specimens for use in the prepara- 
tion of the present volume are due to the same individuals and public 
Vv 
