NO. QO BIRDS OF ISLA COIBA, PANAMA—WETMORE 13 
jay of the mainland (Cyanocorax affinis) does not occur, and there 
are none of the true forest tanagers (Tangara) so abundant as to 
kinds, or of the widespread euphonias. 
The northern end of Isla Coiba is separated from Punta Jabali, 
marking the southern side of the entrance to Bahia Honda, the 
nearest point on the mainland of Veraguas, by a little more than 15 
miles. From the southern end of the island to Punta Brava, at the 
western side of the Golfo de Montijo, the distance is about 32 miles. 
The depths separating the island from the mainland range from 240 
to 330 feet. Coiba is seen thus to be fairly remote in miles, and also 
to be cut off by a fair depth of water. Current geological theory is to 
the effect that the present Isthmus of Panama was considerably 
wider in earlier times than at present. If earth movement during 
the subsidence that has molded the present outline of the land pro- 
ceeded in a fairly regular and evenly distributed manner, then Coiba 
may have been separated early in the history of the Isthmus. If the 
separation came sufficiently early, it may have been established before 
the growth of forests to provide suitable ecological habitat for the 
spread of true woodland inhabitants. Or, the formation of the is- 
land may have come before the missing groups of birds had begun 
their movement between the northern and southern continents. The 
third obvious explanation would be that Coiba at no time was con- 
nected with the mainland. 
While birds are readily mobile because of their powers of flight, 
it is an accepted fact that, although many are venturesome, there are 
many others that avoid crossing wide expanses of water. The avian 
colonists of Coiba in the main appear to be either those that are 
known to make extensive flights, or others—for example, the fly- 
catchers—that may be assumed to have been blown across from the 
mainland by violent winds of tornado force. 
These are purely speculative hypotheses, but it seems difficult ex- 
cept in some such fashion to explain the condition as it actually 
exists. 
ANNOTATED LIST 
Details of occurrence and other information concerned with the 
kinds of birds at present known from Isla Coiba are given, species by 
species, in the pages that follow, with descriptions of the forms that 
are new to science. With each form there is included the scientific 
name with its reference, and a common name in English and in 
Spanish. These common names in the two languages are intended to 
be used for the species as a whole, regardless of geographic race, and 
