| OCR Text |
Show 93 Notwithstanding the wide difference in size between the larger and smaller species of this subgenus, it is absolutely impossible to make a further subdivision of the group, since no characters exist upon which to found such a distinction. Indeed, each species presents greater variations of size and proportions dependent on sex than exist between the majority of the species. For example, in AT. 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, 6.35; tail, 5.50; culmen, 0.35; tarsus, 1.85; middle toe, 1.10, an average difference of nearly one- half in dimensions between the female of cooperi and the male of fuscus; but reversing the sexes, we have, as the minimum measurements of cooperi:- Wing, $. 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, 0.60; 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 \ he inner toe reaching to a little beyond the first joint of the middle toe; bat, in the male of fuscus, it falls considerably short of the first articulation. The* latter has usually the scntellra fused into a continuous plate; bat the female, particularly in the immature stage, has the scu-rellae very distinctly defined. The latter condition is almost universal in cooperi ; but an adult male in our collection ( No. 2554) has as completely u booted " a tarsus as any example of fuscus we have seen. The sexual differences in plumage are inconsiderable, or, practically, inappreciable; but the young and old are entirely different in colors aud markings, there being usually no resemblance whatever, except in the tail, which i? much the same at all ages in each species. It is this feet, and the lack of any other available character to answer the pur- ] K> se, 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 comparative size of the species as well as the limits of variation in each. A * ider 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. Wing. . X » sn » cooperi 8.70- 11.00 . XUus cfaUensts 8.25- 9.90 8.50- 10. 50 8. 60- 10. 50 8.10- 10. 40 8.00- 10.00 6.80- a 40 6. 30- 8. 70 6.25- 8. 00 6.75 a 35- 8.80 7. t50- 7. 80 6.25 Xi « us pnttAtu* Siaua gnndlachi Xisun piteato* Xiso « tricolor Xiiraa chioDoiraAter . . . Ntsiu ventrafls Mmut erythrocDomii.. Xisua ni^ roplnmbeu* - Ninas faicn* Xtsu aaMni KUOJB friogtUoidea Tail. 7.80- 10.50 7.65- 8.50 6.80- 8.50 7.50- 9.50 6.80- 9. 00 7.20- 8.80 6.00- 7.30 5. 40- 7.25 5.40- 6.20 6.30 5. 50- 8.20 6.90- 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. 25- 2. 65 2. 40- 2. 65 2. 50- 2. 75 2. 20- 2. 65 2. 25- 2. 70 1. 90- 2. 25 1. 65- 2.20 1. 55- 2. 00 1.95 1. 85- 2. 30 2.15- 2.20 1. ftO Middle toe. 1.45- 1.85 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 by wide bands of blackish aud |
