YELLOW-GREEN VIREO 323 



despite the abundance of the yellow-green vireo in the dooryards and 

 plantations of men, and the untiring persistency with which it pro- 

 claims its presence during nearly half the year, I have never been able 

 to discover a native name for it, either in Costa Rica or Guatemala. 

 But this lack of a name is hardly surprising in a land where the 

 people as a whole are so indifferent to bird life that kinds so large, 

 abundant, and strikingly beautiful as the trogons are (with the 

 exception of the quetzal) nameless to them. 



Spring. — As one would expect with a bird that comes up from the 

 south, the yellow-green vireo appears latest in the more northern 

 parts of its breeding range. In southwestern Tamaulipas, Mexico, 

 Sutton and Pettingill (1942) did not encounter it before April 9. 

 During mid-April it became steadily commoner, until, by the 20th, 

 it was abundant. It began to sing as soon as it arrived. In Guate- 

 mala, according to Griscom (1932) , it arrives "the first week in April, 

 earliest record late March (Dearborn), but is not generally common 

 or singing until April 15." In central Costa Rica (San Jose) it arrives, 

 according to Cherrie (1890), in the middle of April. But here in the 

 Terraba Valley of southern Costa Rica, nearer its winter home in 

 South America, it commonly appears early in February. In 1936 1 first 

 recorded it at Rivas (3,000 feet) on February 6; the following year, 

 on the 4th ; in 1939, on the 8th. In 1942 I first saw the bird at General 

 Viejo on February 15 but heard its voice several days earlier. No 

 sooner have the males arrived than they begin to advertise their re- 

 turn by their song. Since they remain well concealed in the crowns of 

 the full-foliage trees, one is usually first apprised of their home- 

 coming by their voices. Rapidly increasing both in numbers and 

 tunefulness, they are soon singing everywhere along the shady roads 

 through the cultivated districts, the pastures with scattered trees, and 

 the rivers overhung by the epiphyte-laden boughs of the spreading 

 sotacaballo. Their song so greatly resembles that of the red-eyed 

 vireo that, to one newly arrived from the north, their voices lend a 

 homelike touch to an otherwise strange environment. 



Nesting. — Just how the yellow-green vireo wins his mate has so far 

 escaped me. At this season, when a score of birds in the surrounding 

 forests are preparing nests never seen by ornithologists, so familiar 

 a bird is apt to receive far less attention than it deserves. Before one 

 is aware of it, he has paired and his mate is beginning to build. My 

 earliest date for the beginning of nest construction is March 18, 1937, 

 a year when rains were frequent the first three months, which here 

 are normally dry. The first egg was laid in this nest on March 27; 

 but my next early record for eggs is April 24 of the same year. Here 

 in the basin of El General (the head of the Terraba Valley) , between 

 2,000 and 3,000 feet above sea level, nests with eggs are not easily found 

 before May, which is the height of the breeding season for this bird, 



