392 



Chapman, A Hybrid S-wallo-v. 



TAuk 

 LOct. 



A HYBRID BETWEEN THE CLIFF AND TREE 

 SWALLOWS. 



BY FRANK M. CHAPMAN. 



The American Museum of Natural History has recently acquired 

 from the collector what seems to be a hybrid between Petrochclidon 

 Iwiifrons and Tachycineta bicolor. The specimen (No. 78,119 

 Springfield, Mass., Aug. 20, 1902, Leon C. Holcomb) is apparently 

 a bird of the year and, in addition to presenting evidences of 

 hybridism, exhibits also albinistic characters, though it is possible 

 the latter may be a result of hybridity. Generally speaking this 

 specimen resembles bicolor below and hmifrons above, the rusty 

 and buff markings of the last named species, however, being, in 

 this supposed hybrid, white. A more definite understanding of 

 this interesting bird's color and markings may be gathered from 

 the appended comparative tables : 



Form. 



T. bicolor. $ im. 



Medium ; width at nos- 

 tril 4.5 mm. Nostril el- 

 liptical; a well-developed 

 operculum. 



Long, 118 mm. 



Hybrid. ^ im. P. lunifrons. $ im. 



Bill. 



Medium; width at Rather heavyand broad; 



nostril 4.5 mm. Nos- width at nostril 6.3 m. 



tril circular; a well- Nostril circular; no 



developed operculum, operculum. 



Wing. 

 Short, 103 mm. 



Tail. 



Medium, 105 mm. 



Medium, 50 mm.; fork, Short, 40 mm.; fork, Medium, 45 mm.; fork, 



9 mm. deep. 4 mm. deep. 2 mm. deep. 



Feet. 



Slender, tarsus 11 mm.; Medium, tarsus, n Rather stout, tarsus, ii 



middle-toe, II mm.; nail, mm.; middle-toe, 11 mm.; middle-toe, 11 



4 mm. mm.; nail, 3 mm. mm.; nail, 5 mm. 



