RIEFFER'S HUMMINGBIRD 435 



records of nests, from one part or the other of this region, for each 

 of the 12 months. In the Province of Bocas del Toro in western 

 Panama the majority of the nests were discovered during the drier 

 weather from January until May. Although in the lowlands the 

 nesting period, for the species as a whole, is unusually long, even for 

 tropical birds, and is peculiar in including both the dry and rainy 

 seasons, we do not know how many broods each female may raise 

 in a year, or what period the breeding activities of a single individual 

 may cover. 



At Rivas, on the Pacific slope of southern Costa Rica, the hum- 

 mingbirds of several species, including Rieffer's, behave in their 

 choice of a breeding season essentially as the members of the family 

 that dwell in the higher mountains, although here the altitude is 

 only 3,000 feet and the avifauna in general is that of the humid 

 lowlands, with a slight admixture of species representative of the 

 subtropical zone. In this region there is, in most years, a pronounced 

 dry season of four months, from December to March, inclusive, 

 while the remaining eight months are very wet. The great majority 

 of birds of all kinds breed between the vernal equinox and the June 

 solstice; but there is a scattering of nests of birds belonging to the 

 most diverse families at all periods of the year. The hummingbirds, 

 however, breed chiefly during October, November, December, and 

 January, the very months when nests belonging to birds of other 

 families are fewest. 



During a residence of a year and a half at Rivas, I recorded six 

 nests of Rieffer's hummingbirds during November, December, and 

 January but not a single one during the other nine months, when 

 nests were just as assiduously sought by myself and the boys I had 

 reporting them to me. Flowers, although many are to be found 

 throughout the year, reach their maximum profusion in the clearings 

 during December and January, and their minimum abundance at the 

 end of the dry season in March. 



The highest point at which I have seen a nest of Rieffer's humming- 

 bird is the Hacienda Las Concavas, near Cartago, Costa Rica, where, 

 at an altitude of 4,500 feet, I found a nest with two well-feathered 

 nestlings on November 3, 1935. The bird was nesting in the wettest 

 and least agreeable season of the year, at a time when scarcely any 

 of the Central American bii-ds of other families breed at so high an 

 elevation. 



The nests of Amazilia are placed in trees or bushes in the clearings 

 where the birds reside, without any distinct preference for any par- 

 ticular type. Frequently a thorny lime or orange tree is chosen, or 

 a bougainvillea vine ; but as often a thornless kind is selected for the 

 nesting site. Sometimes even a low herbaceous plant is favored. I 



