FAMILY TROCHILIDAE 337 



posed that they were Rieffer's hummingbirds (Amazilia tsacatl 

 tzacatl), common on the adjacent mainland, and recorded them under 

 that name in an account of the avifauna of the island (Wetmore, 

 Smithsonian Misc. Coll., vol. 139, no. 2, 1959, p. 6). 



In further studies of the fauna of Escudo, Dr. Charles O. Handley, 

 Jr., of the U. S. National Museum, through cooperation of the U. S. 

 Army visited the island in 1962, and lived there in a shore camp 

 from March 20 to 24. Though his visit was directed toward collec- 

 tions of the mammals of the island, in addition he and his assistant 

 Frank M. Greenwell, preserved a number of birds, some shot for 

 specimens, and others caught in mist nets set for bats. Five of the 

 hummingbirds referred to above as seen during my own visit in 

 1958 were captured in nets set across the mouth of the lagoon at 

 the eastern end of the island. The specimens, preserved originally 

 in formaldehyde, on their arrival in the museum were prepared as 

 skins by Mrs. Roxie Laybourne. In the hand, it was obvious that, 

 though they resembled Rieffer's hummingbird in brown tail and general 

 color pattern, they were so much larger in all dimensions, especially 

 in bulk of body, and so dark in color, that they represented a form 

 previously unknown. Amazilia tzacatl in its wide distribution from 

 eastern Mexico to Colombia, northwestern Venezuela, and western 

 Ecuador, as a species is uniform in size, with the only marked varia- 

 tion in color a wash of buff on the abdomen in the population of 

 southwestern Colombia and western Ecuador (recognized as stated 

 above as a subspecies Amazilia t. jucunda). In much greater size 

 the five birds from Escudo are so different that this island group is 

 treated as a separate species, distinction given further weight by the 

 coloration, that has no approach in the birds of the mainland. 



To make certain that the color differences were not due to the 

 method of original preservation I placed a study skin of Amazilia t. 

 tzacatl in the same fluid in which the hummingbirds from Escudo 

 had been received. When dried after a month of immersion this 

 specimen showed no signs of change, nor have any appeared in the 

 5 years that have followed to the time when the present account was 

 written. 



The feathers along the side of the neck when the birds were wet 

 from the original preservative appeared metallic reddish purple, a 

 color that disappeared completely as the birds dried. The same 

 color appeared in this area of the neck in the skin of Amazilia t. 

 tzacatl when the preservative wet its feathers. This also disappeared 

 when the specimen again was dry. 



