348 U. S. NATIONAL MUSEUM BULLETIN 211 



of a quick snap and hardly wetting their plumage in the process. At 

 other times, however, these grackles plunged boldly into the lake, like 

 a tern or a kingfisher, immersing themselves to a depth of not more 

 than 3 or 4 inches. Sturgis (1928) records that the great-tailed grackles 

 frequent the most isolated rocks in Panama Bay, where doubtless they 

 devour a variety of small marine creatures. In Costa Rica, Carriker 

 (1910) found the bird common among the mangroves of the brackish 

 estuaries so numerous along the Pacific coast. 



Like other grackles, this species pillages the nests of other birds, 

 devouring their eggs or nestlings. In Guatemala, I surprised a male 

 boat-tailed grackle resting upon a fence-post where a pair of Bona- 

 parte's euphonias (Tanagra lauta lauta) had built a nest, well concealed 

 in a cranny caused by decay. The roof had been torn from the little 

 domed nest and the newly laid eggs had vanished. Although I arrived 

 too late to catch the grackle in the act, the circumstantial evidence 

 pointed strongly toward him as the despoiler of the nest and-devourer 

 of the eggs. In Mexico, Chester C. Lamb (1944) saw a male grackle 

 seize a female yellow warbler which had dashed into the face of the 

 bigger bird in a vain attempt to save her eggs. The warbler was killed, 

 her skull crushed by the grackle's powerful bill. 



Of vegetable food, the grackles are fond of ripe bananas and of 

 small, sweet berries, especially those of the melastomaceous shrub 

 Conostegia. They greedily eat maize, tearing up the germinating 

 grains from newly planted fields. One Guatemalan farmer told me that 

 his efforts to start a cornfield were frustrated by the grackles until he 

 adopted the expedient of scattering a considerable quantity of grain 

 about the edges of his field. This kept the hungry birds occupied until 

 the planted maize had grown large enough to withstand their attacks. 

 Yet this same farmer considered that the grackles, by destroying grubs 

 and other insect pests, did on the whole more good than harm on his 

 estate. Later, as the maize crop nears maturity, the grackles renew 

 their depredations upon the milpas, tearing open the husks to reach 

 the tender, milky grains, which the females at this season feed to their 

 fledglings. 



Behavior. — The big male grackle glides downward with wings set, 

 the tips of the primaries separated from each other and distinctly 

 curved upward by the weight of his heavy body, and with his long 

 tail folded together upward so that the feathers lie in a vertical plane, 

 like that of the purple grackle, and vibrating from side to side in the 

 breeze. Usually he flies upward with heavy, resonant wing beats, like 

 those of the male oropendola; but at times he may fly silently. The 

 flight of the female grackle is almost silent; but when laboring upward 

 with long fibers for the nest streaming from her bill, her wing beats 



