NO. 9 BIRDS OF ISLA COIBA, PANAMA—WETMORE 47 
bloom the birds congregated about them in some numbers. A female 
shot January 11 was laying. The three males and three females pre- 
pared for specimens agree with mainland examples. 
AMAZILIA TZACATL TZACATL (De la Llave): Rieffer’s Hummingbird, 
Colibri Colimorena 
Trochilus Tzacatl DE ta Liave, Registro Trimestre, vol. 2, No. 5, 1833, p. 48. 
(México.) 
This species, easily identified by the rufous-brown tail, is the most 
abundant hummingbird, ranging from the open borders of the low- 
land swamps back into the heavy shade of the high forest. They 
were especially abundant at the flowers of the white mangroves, and 
at the blossoms of the guayabo trees growing in the open, but were 
observed elsewhere at almost any herbaceous plant or shrub that 
was in bloom. The flowers of the mangroves were so large that to 
feed on them easily the hummers usually perched on the ends of the 
petals, or on adjacent blossoms, and then reached over with long bills 
to probe the centers. In early morning I found this hummingbird in 
the warm sun on open branches, often in small dead trees along the 
beaches. Part at least were nesting during January, and I was in- 
terested to have one male scold me with loud chirping calls. On Janu- 
ary 8 I found a nest in a small, broad-leafed tree growing beside a 
coconut palm back of the beach. The bird had built on a shaded 
horizontal branch about 7 feet from the ground, the entire structure 
being formed of fine shreds of plant fiber, of coarser form exteriorly 
on the immediate surface, but aside from this quite uniform. The 
outer surface was light grayish brown, decorated with a few bits of 
lichen. The nest measured 42 by 44 millimeters externally, being 
somewhat flattened by the two well-grown young, a week or more 
old, that it contained. These had two lines of clay-colored down 
along the dorsal pteryla. The female perched on the edge of the nest 
beside them, striking steadily with her bill at large ants that ran back 
and forth along the branch supporting the nest. This hummer was 
common also on Isla Rancheria. 
The series of 12 adult birds, viewed as a whole, averages very 
faintly darker on the lower breast and abdomen than the excellent 
representation available from the mainland. None of the Coiba birds 
is as light as the average from Panama proper, but numerous speci- 
mens from the mainland are equally dark. The island series also is 
uniformly deep green above, again being equaled by occasional skins 
