300 REPORT OF NATIONAL MUSEUM, 1800. 



Variatiom in the form of the tail. — Tlio miinber of tail-featbers is 

 usually, ]HHliaps always, ten. One species, the Marvellous Humming 

 Bird {/jO(l(li(j('sia wirahilis), is said to possess only four; but, although 

 1 have not seen the bird in question, I can not help thinking that the 

 ai)parently absent rectrices are abojted and confounded with the 

 <;overts.* Certainly in at least one other genus (Mi/rtis), such au abor- 

 tion of the middle pair of tail-leathers is very evident, these being so 

 much reduced in size as to be entirely concealed by the upper tail- 

 coverts.t On the other hand, another genus (Florisfiga) seems to pos- 

 sess twelve tail-feathers; but a close examination will show that what 

 are apparently the middle pair of rectrices are in reality the two longest 

 upper tail-coverts. 



Fio. 26.— Tail of MiiHin fanny. Hliowiiitt Fia. 27.— Tail .if Florisuga mellivora, showing 

 alxn'tod niiihllo Voctrictvs \.r x), i\w specialized pair of upper coverta (a a), 



upprr tiiil-oovorts beiiiu piutod (o ex- 

 pose tluMu to view. 



The shape and development of the tail-feathers in the Humming Birds 

 vary to a degree that has no parallel among other birds, many of the 

 forms assumed being also entirely unique. Much the larger number 

 of species have the tail of a shape not very dilferent from the ordinary 

 types among birds, that is to say, moderately rounded or forked, or 

 nearly even ; but besides tails of a normal shape there are deeply 

 forked or forUcate (scissors shaped) tails, graduated or wedge-shaped 

 tails, double-rounded and doubleemarginated tails, tails with streamers, 

 tails with racket- or paddle shapeil feathers, and tails whose shape can 

 not be designated by any special term, l^utting aside those which 

 depart least from the ordinary shapes, the dift'erent types, with their 

 variations, are illustrated by the ligures composing Plates xviii-xxiv. 

 Vanations in development of the tailcoverts. — Excepting the case of 

 Florisu<)n, referred to above, there are few notable moditications of the 

 tailcoverts. Two genera, however, may be mentioned which have these 

 feathers conspicuously developed, the one as to size, the other as to 



* In Aoestrum miornra, accordini:; to Mr. Gould, all tbo rectricos aro tluus aborted, 

 tho entire tail boins; concoalod by tbo coverts. 



t Gould also citea as examples Thaumaatara cora and Doricha enicura ; but in tbese 

 species tbo middle pair of rectrices wbile very sbort aro not wbolly bidden by the 

 coverts, as is tbo cvse in Miirlisfaninj. (See Plate xxiv, Fig. 1, and Plate xxii, Fig. 1). 



