474 PROCEEDINGS OF THE NATIONAL MUSEUM vol. i04 



The status of North American migrants calls for some comment 

 here. Davis (1954, p. 441) reports that in an inland area of British 

 Guiana northern migrants are scarce both in numbers and in kinds. 

 Only some 40 North American species, excluding rare or accidental 

 vagrants, are known from all of British Guiana, nearly half of them 

 being shore birds. Comparing observations with those in our earlier 

 report, Davis rightly concludes that in this respect his part of 

 British Guiana is essentially similar to our area in northeastern 

 Venezuela. He adds that the reason why the South American tropics 

 are not a more important wintering area for northern migrant land 

 birds may be that Central America, where these migrants swarm in 

 great numbers, provides sufficient suitable winter quarters to take 

 care of most of these northern wanderers. ". . . It is improbable that 

 suitable habitats are not available in tropical South America, for 

 even if the heavy rain forest is avoided, there are savannas, cultiva- 

 tion, and the forest edge, both in conjunction with such open areas, 

 and along thousands of miles of river. ..." 



It should be kept in mind, however, that seasonal suitability of 

 terrain is a factor to be considered with, although not in place of, that 

 suggested by Davis. In our area the time of year when the northern 

 birds are wintering, roughly September through April, is the dry 

 season when the lowlands are parched and the greenery is confined 

 to a very thin strip along the rivers. Thus, although in the wet season 

 many places would seemingly be suitable for these northern visitors, 

 they would be not at all suitable during the dry season. 



The junior author notes that in western Venezuela (upper Apure, 

 Barinas) the blue-winged teal is very numerous, apparently because 

 the habitat there is suitable, while in the east, where the land is so 

 much dryer, it is much scarcer. Our area is one where, because of the 

 unfavorable nature of the countryside during the dry season, most 

 migrant land birds would not or could not stay. The one important 

 exception to this rule is the dickcissel Spiza americana, which occurs 

 in flocks of 500 to 1,000 in the dry-brush savanna-edge habitat. 

 However, in its breeding range it is a bird of fairly dry fields and 

 bush-lined roads and thus may be better adapted to the Venezuelan 

 lowlands during the northern winter than are most other North 

 American migrants. Numerically, it may be one of the most important 

 Nearctic migrants to Venezuela, but curiously it seems not to have 

 been recorded from the part of British Guiana studied by Davis, 

 perhaps because that area is east of its winter range (there is but a 

 single record for the bird in British Guiana, the Abary River). 



This same area of northeastern Venezuela, which seems so unsuit- 

 able to northern migrant land birds in the dry season, supports during 

 the wet months (July through September) vast numbers of a migrant 

 from south of the tropics, the fork-tailed flycatcher Muscivora tyrannus 



