124 IXlIKKITAXf-E, FERTILITY, AND SEX IN PIGEONS. 



pair (table 107) is formed of a complex Zenaida-Zenaidura hybrid mated to a 

 complex risoria-alba hybrid. 



It is clear that some of these matings are more fertile than are others; but it is 

 not at all apparent that the primary cross is more fertile or less fertile than the 

 crosses of the hybrids. The differences in the fertility of individuals is doubtless a 

 complicating factor here. The dissimilar distribution of the eggs over the seasons, 

 and unequal overwork for some pairs, are other variables which make a comparison 

 difficult. It may usually be observed, however, that there is a much decreased 

 fertility after July. 



From none of these matings were female offspring obtained. The matings in 

 which pure females were used yielded 16 males and the hybrid females 6 males. It 

 is of interest to note the number and proportion of young possessing no sex-glands 

 which arose in these fraternities. The pure female parents that gave 16 males 

 produced 1 such young; the hybrid females produced in addition to 6 males, 3 

 offspring with no gonads, and another with very minute testes or testis-like bodies. 



Since the mourning-dove and the mourning x Zenaida hybrid have several 

 very sharply defined color-marks or spots and the blond ring has a uniform colora- 

 tion, it is of interest to note some features of color inheritance in these hybrids. 

 The mourning-dove is shown in pi. 19; the blond ring has been already seen 

 in pi. 8. The following description applies to one of the hybrids (<?H1 of 

 April 24, 1900, of table 101) of these two forms. 



With regard to "the spots on the tertials it would seem at first sight as if there 

 were 'no traces' whatever. On lifting the feathers, about 3 of the upper tertials 

 are found to have 'dusky areas' on the inner webs, with no distinct outlines, but 

 corresponding in position with the elongated spots of the mourning-dove." 



There are no distinct spots on the lesser coverts, but some of them, when lifted, display 

 on the basal half a dusky gray in the place of the spots found in the mourning-dove. These 

 dusky-gray areas are often quite clearly outlined or bounded distally, like the "imprints" I 

 once discovered in the white-wing pigeon (Melopelia). 



At first glance it would be thought that there is no ring and no iridescence in the hybrid. 

 On closer view, I see that about 4 rows of feathers on the side of the neck (corresponding to 



EXPLANATION OF PLATE 20. 



A. Juvenal male Zenaida-Zenaidura x Streptopelia risoria hybrid (ZZ-R 1). Hatched from egg of 



May 3, 1908 (table 105). Seven-tenths natural size. K. Hayashi del., July 1908. 



Sire: Zenaida x Z< iiniiliira hybrid (7//, 1 of this plate). Dam: >S7. rixoriu. 



The juvenul feathers ure much as in Juvenal mourning-doves, but considerably lighter (pale edges as in the mourn- 

 ing-doves and ring-doves) and the spots are fewer and duller. \'i'stiyes of spots are found on the outer web of the inner 

 tertials and on the inner large coverts. The tail feathers are 12 in number (as in the dam); the two mid-feathers are 

 0.25 inch longer than other rectrices (this is intermediate to the mourning-doves and the ring-doves), but are rounded 

 (this is toward Zenaida and riwria) rather than pointed. 



B. Adult male Zenaida x Zenaidura hybrid (ZZ 1). Hatched from egg of April 10, 1905 (table 91). 



Seven-tenths natural size. K. Hayashi del., May 190G. 



In the juvenul plumage the feathers of the back, wings, neck, breast, and forehead were pale-edged, as in Zenai- 

 i/iini. Two dark streaks are present on the sides of the head, above and below the ear-coverts. Legs pale red. The 

 black spots are not quite so numerous as on young mourning-doves. The ground color is that of young mourning- 

 duves, but with a shade more of the reddish brown of Zenaida. On the breast feathers (Juvenal) there is a reddish 

 mid-streak (as in Leptopttia), which is wider at the tip and gradually narrowed inward to a point. The reddish is 

 seen at the middle of the tips of the primaries, though there it is not regular in form as on the breast; this also seen 

 in the primary coverts. // looks us if tliix were OK- mil/ the bl/icl. n-nter birnnic dirided intoltro lateral spots. If so, it is 

 essentially as in the common pigeon and in ('. lirin. The nest -mate (ZZ 3) of this bird was quite similar to it. 



