98 ORTHOGENETIC EVOLUTION IN PIGEONS. 



This simple mode of converting the turtle-dove spot into a pair of lateral 

 chequers is carried out most perfectly in the posterior scapulars and in the inner 

 secondaries and large coverts of the wing of the domestic pigeon. As we pass down- 

 ward towards the lower (outer) edge of the wing, the chequer on the inner web 

 diminishes in size more or less rapidly and may be continued to or near the outer 

 edge of the wing. 



Now, chequers are the elements out of which wing-bars arise. "Rows of 

 chequers," as we see them in the young mourning-dove or in the young passenger- 

 pigeon, or in the chequered rock-pigeon (Columba affinis), may of course be called 



EXPLANATION OF PLATE 42. 



A. Cape-pigeon, female Oena capensis. Toda del., after Temminck and Knip, Les Pigeons, i, 



p. 117, pis. LIII and LIV, 1808-1813. x ? 

 Temminck and Knip picture both male and female. 



A very interesting species for comparison with the crescent-barred geopelias. It is much more highly differ- 

 entiated than any of the geopelias in that: 



(1) The male is differently colored from the female, having its (a) forehead, throat, front neck, and breast black; 

 (b) the occiput and hind neck are pale brown shading into pearl-gray on the sides of the neck (the female has the whole 

 head and neck and breast pale brown, becoming lighter in front half of head and throat) ; (c) ''the inner upper wing- 

 coverts have large steel-blue patches" (Salvadori), which are not seen on the female. These spots remind of the 

 Florida ground-dove. 



(2) The dark crescents have all disappeared except in the upper tail-coverts (possibly the few black bands on 

 the lower back are derived from the crescents), where they are still preserved in both sexes. 



(3) The great length of the middle tail-feathers. 



(4) The 2 (4 in female? Temminck says 3 bands) black bands across the lower back. 



According to Salvadori (p. 503), the young has dark crescent-bars on crown and neck, and the wing-coverts are 

 grayish-brown, with blackish crescentic bars and light buff edges. 



The pictures (of Madame Knip) of the adult male and female show that the crescents are apical in the male and 

 subapical in the female, the female seeming to keep the pale edge of the young. 



B. Right wing of adult female tambourine-dove, Tympanistria tympanistria. Natural size. Drawn 



from U. S. Nat. Mus. No. 116316. 



Here we find in the tertials 2 plain spots and 1 very weak spot, ordinarily concealed, and perhaps not always 

 present. 



In the long coverts 3 plain spots one more than in the Juvenal male, an indication that female has more spots 

 than male. 



In the first row of median coverts we have two concealed spots, seen by lifting the overlying row. These were 

 not found in the Juvenal male. (The single Juvenal bird examined is elsewhere stated (see figs. C and D) to be a female. 

 I am quite unable to understand this and the earlier reference to a "Juvenal male"; unless perhaps a figure or descrip- 

 tion by Dr. Butler (?) of such a bird was at hand. -En.) Again an indication that spots are more numerous in the 

 female than in the male. 



No spots in the scapulars, and no spots or streaks on the inner webs. These spots extend towards the base of 

 the feather, as in the Juvenal. 



There is probably more pigment in the adult (permanent) spots, but I should expect to find in the young female 

 a little larger number of spots than in the adult. 



C. Three inner tertials of Juvenal female tambourine-dove. Drawn from U. S. Nat. Mus. No. 117867, 



July 1907. 



Shows rufous apical marks (of 1 to 1.3 mm.) followed by a dark bar, darkest next to the apical mark. 



The dark bar is narrow (1 mm.) at the margins and wider (up to 3 mm.) near the feather's shaft. This dark 

 bar is followed by a narrow irregular rufous bar. 



Shows also black chequer on the outer web; these are squarish, on the margin and about 10 mm. from tip in first 

 feather, 15 mm. in second feather. Only two chequers in this row; size is about 7 by 6 mm. 



D. Two inner long coverts from same bird as above. 



In the long coverts I also find only 2 spots, but these extend farther towards the base of the feather and thus 

 show that the chequers are derived from the dark center of the turtle-dove feather. 

 For a description of general ground-color see Butler, Avic. Mag., Aug. 1906. 



E. Wing of adult male Chalcopelia afra. Natural size. Hayashi del., Aug. 1904. 

 This species forms one of the color-types connecting the turtle-doves with Geopelia. 



Compare with Pmxlera cinerea (pi. 31) and with open wing of another adult male C. afra (pi. 35, fig. B), where 

 the legend applies also in part to the present figure. 



