FAMILY TROCHILIDAE 305 



there are flowers. Mainly they are flower feeders, found with other 

 species of the family at shrubs and trees like the guayabo, but also 

 searching out smaller blossoms, often near the ground. They also 

 glean branches and tree trunks. It is not uncommon to find them in 

 the more open areas in gallery forest, and in coffee when in bloom. 

 They come regularly into towns, where flowers attract them to orna- 

 mental hedges and open patios. 



Little is recorded of their breeding. A female taken on Isla Coiba 

 on January 16, 1956, was laying. On March 13, 1948, at La Cabuya, 

 Herrera, I secured birds with enlarged gonads. Mrs. Sturgis (Field 

 Book Birds Panama Canal Zone, 1928, p. 192) recorded nests at 

 Quarry Heights, Canal Zone, in November 1924, and January 1923. 



The female and the immature male of this species in life may be 

 confused with those of Lepidopyga cocraleogularis, or of the smaller 

 Damophila julie, but are identified by the whitish spot back of the eye, 

 a mark that is not present in the other species mentioned. 



On Isla San Jose on an early morning in late February when 

 the thermometer fell to 69.5° Fahrenheit, in the strong breeze the 

 air was cold. Soon after sunrise I found a male hummingbird of this 

 species fluttering on the ground chilled and unable to fly so that I 

 caught it in my hand. 



Zimmer (Amer. Mus. Nov., no. 1474, November 10, 1950, pp. 

 6-12) has united the numerous mainland forms of emerald humming- 

 birds that as a group range from southern Mexico to northern Brazil, 

 under a single specific name, Chlorostilbon mellisugus (Linnaeus). 

 This is a simplified procedure of a complex problem of relationships 

 but one that, after considerable study based on extensive series of 

 specimens, does not impress me as logical. As a general statement 

 it would seem that division into a number of species, as proposed by 

 Simon (Hist. Nat. Trochilidae, 1921, pp. 57-68) in major part may be 

 more reasonable. 



Viewed as a whole, the numerous populations may be separated 

 into two groups on bill color, one in which the bill is wholly black, 

 and one in which the basal part of the mandible in life is orange 

 or orange-red (fading to a paler tint in museum skins, but always 

 evident). This clearcut difference is found in both sexes, and does 

 not vary within the separate populations. The distinction would 

 seem to present a major character for group recognition between 

 individuals. In Central America from Mexico through most of 

 Costa Rica the five populations now recognized as allied subspecies 

 have the bill base light. In southwestern Costa Rica and most of 



