OTHER PIGEON HYBRIDS AND BREEDING OF CERTAIN SPECIES. 165 



(table 162). The data for fertility of the Senegal x blond and white ring crosses, 

 both in the primary cross and in the resulting hybrids, is therefore higher than will 

 be found in the family cross next to be considered. It will soon appear that the 

 sex-ratio from the two groups of crosses — genera and family — ^furnishes a parallel to 

 this difference in fertility. Where infertility is greatest, and the cause of this infer- 

 tility is width of cross, the ratio of males to females is also highest (table 167). 



Migratorius x risoria and alha-risoria hybrids. — Two crosses of these forms, 

 which are separated by differences of family rank, showed a high percentage of 

 infertility; several embryos incapable of hatching were formed; and a notable frac- 

 tion of the young died very soon after hatching. The 8 offspring which survived 

 were all males (table 165). 



The male species concerned in this mating is the now extinct wild American 

 passenger-pigeon. The above-described hybrids, together with the two listed 

 immediately below, are perhaps the only known hybrids of this remarkable species. 

 The male passenger-pigeon is shown in pi. 28, the female in pi. 29, and one of the 

 hybrids from the migratorius x alha-risoria x risoria-alha cross is also shown in pi. 30. 

 The intermediate nature of the hybrid becomes clear from an insjiection of the 

 illustration. This topic is further discussed in Chapter XVH. 



Migratorius x alba. — This record is short, though similar to the preceding. Two 

 males were produced. The very first egg of the series and the last 3 of the season 

 were w holly infertile. 



Miscellaneous crosses. — The three crosses listed in table 166 require but little 

 additional discussion. The damarensis x risoria-alha cross (pair 1) is a mating of 

 related species, and the fertility seems high and the term of life moderatel}^ long. 

 The chinensis x suratensis mating (pair 2) is also one between related species of the 

 genus. The fertility record here falls below that of the preceding cross, and the 

 term of life of the offspring is shorter. The leuconota x livia cross (pair 3) tells us 

 only that offspring may be had from this cross. The last of these crosses (pair 4 of 

 table 166) supplied more adequate tests and is of greater interest. The genera 

 involved in that cross — Melopclia and Streptopclia — belong to different subfamilies, 

 and the table indicates again the very high degree of infertility of such crosses. 

 Only three birds were hatched from the 18 or 20 tests; there were produced, more- 



Table 161. 

 d' Senegal. -risoria (TS-R 2). 4/10/0'J; 2/26/11; 22 mo. 

 9 St. alba; age unknown. 



A 1. 5/15/10 TSRA 1 disappeared 2/5/11 to 11/4/13. 



B 1. 7/24 TSRA 2 darker than B 2; disappeared 7/5/11 to 11/4/13. 



9 B 2. 7/26 TSRA 3 light ruddy blond; dead 5/7/13. (AA 6 



Table 162. 

 (? Seneg.-risoria hyh. (22) ; 8/8/09; 11/28/11; son; pale yellow eye. 

 9 St. risoria (O): age unknown; dam; yellow eye. 



A 1. 4/16/10 TS-RRl disappeared 7/5/11-11/4/13 (or, died ? 9 7/28/13; darker than A 2). 



A 2. 4/18/10 TS-RR2 disappeared 7/5/11-11/4/13 (or, is c? or cf 9 alive 10/1/14; lighter than A 1). 



Bl. 5/29 TSRRl disappeared 7/5/11-11/4/13 (or, died ?9 7/28/13). 



B2. 5/31 TSRR2 disappeared 7/5/11-11/4/13 (or, is c? or cf 9 alive 10/1/14). 



CI. 6/30 TSRR3 disappeared before 7/5/11. 



?crC2. 7/2 TS-RR4 alive 10/1/14; is a c?, or hermaphrodite. 



D 1. 9/5 TS-RR5 probably died early; darker than D 2. 



D2. 9/7 TS-RR6 probably died early; lighter than D 1. (AA 7) 



