93 



Notwitlistandinc;" the wide difference in size between tlie lar^^er and 

 smaller species of this subgenus, it is absolutely impossible to make a fur- 

 ther subdivision of the group, since no characters exist upou which to 

 found such a distinction. Indeed, each species presents greater variations 

 of size and proportions dependent on sex thau exist between the majority 

 of the species. For example, in N'. cooperi, one of the larger species, the 

 maximum measurements are: — Wing, 11.00; tail, 10.50; culmen, 0.80; 

 tarsus, 2.85 ; and middle toe, 1.85 ; while in N.fuscus, one of the smaller 

 species, the minimum is: — Wing, G.35; tail, 5.50; culmen, 0.35; tarsus, 

 1.85 ; middle toe, 1.10, an average difference of nearly one-half in dimen- 

 sions between the female of cooperi and the male of fusciis; but reversing 

 the sexes, we have, as the minimum raeasuremeuts of cooperi: — Wing, 

 8.70; tail, 7.80; culmen, 0.58; tarsus, 2.30; middle toe, 1.45; and as the 

 maximum of fuscus: — Wing, 8.80; tail, 8.20; culmen, O.GO; tarsus, 2.30 ; 

 middle toe, 1.55 — the conspicuous difference being thus completely lost. 

 As regards proportions of the toes, the male of cooperi and the female 

 of fuscus (typical representatives of the two extremes of size) have the 

 inner toe reaching to a little beyond the lirst joint of the middle toe; 

 but, in the male of fuscus, it falls considerably short of the first articu- 

 lation. The latter has usually the scutellse fused iuto a continuous 

 plate ; but the female, particularly in the immature stage, has the scu- 

 tellte very distinctly defined. The latter condition is almost universal 

 in cooperi; but an adult niale in our collection (Xo. 2554:) has as com- 

 pletely "booted" a tarsus as any example of fusc^is we have seen. 



The sexual differences in plumage are inconsiderable, or, practically, 

 inappreciable; but the young and old are entirely different iu colors 

 and markings, there being usually no resemblance whatever, except in 

 the tail, which is much the same at all ages in each species. It is this 

 fact, and the lack of any other available character to answer the pur- 

 pose, that has induced us to attach so much importance to the tail- 

 bands in our key to the species. 



The following table of measurements will serve to show the compara- 

 tive size of the species as well as the limits of variation in each. A 

 wider range would doubtless be shown in several of these had we a 

 larger series for measurement, there being in the annexed table one or 

 two instances where but one sex is represented. 



Comparative measurements of American species- of Nisus. 



Xisns 

 Nisus 

 Xiaus 

 Xisus 

 Xisus 

 Xisns 

 Xisus 

 Xisus 

 Xisus 

 Xisus 

 Xisus 

 Nisus 

 Nisus 



Wing. 



cooperi 8. 70-11. 00 



cbilensis 8. 25- 9. 90 



guttatns I 8. 50-10. 50 



ffundlachi S. 60-10. 50 



pileatus I 8.10-10.40 



bicolor I 8. 00-10. 00 



chiouo'iaster ' fi. 80- 8. 40 



veutralLs 



ervtlirocneuiis. 

 uigroplumbeus 



fnscu.s 



-salvini 



trinKilloidcs. .. 



6. 30- 8. 70 



C. 25- 8. 00 



6.75 



6. 3.T- 8. 80 



7. 60- 7. 80 



6.25 



Tail. 



7.80- 

 7.65- 

 6.80- 

 7.50- 

 6.80- 

 7.20- 

 6.00- 

 5.40- 

 5.40- 



5. 50- 

 6.90- 



10. 50 

 8.50 



■ 8.50 

 9.50 

 9.00 



■ 8.80 

 7.30 

 7. 25 

 6.20 

 6.30 

 8.20 

 7.00 

 4.80 



Culmen. 



Tarsus. 



0. 58-0. 80 

 0. 50-0. 70 



0.60 



0.68 

 0. 50-0. 70 

 0. 55-0. 75 

 0. 40-0. 52 

 0. 35-0. 55 

 0. 35-0. 45 



0.45 

 0. 35-0. 60 



0.50 



2. 30-2. 85 

 2. 2.5-2. 65 

 2. 40-2. 65 

 2. 50-2. 75 

 2. 20-2. 65 

 2. 25-2. 70 

 1. 90-2. 25 

 1. 6.1-2. 20 

 1. 55-2. 00 



1.95 

 1. 8.5-2. 30 

 2. 15-2. 20 



1.80 



Mitldle toe. 



1. 45-1. f 5 

 1. 40-1. 70 



1. 35-1. 70 

 1. 45-1. 80 

 1. 30-1. 55 

 1.10-1.50 

 1. 10-1. 40 

 1.30 

 1.10-1.55 

 1. 45-1. 50 



The following key to the species is the best we have been able to 

 devise from very complicated and variable characters presented. The 

 characters common to all the species are the following: — 



Common characters. — Tail crossed bv wide bands of blackish and 



