FAMILY ICTERIDAE 



357 



vol. 42, 1929, p. 123) is responsible for dividing this species in Middle 

 America, and he also recognized the race violea Bangs, which Hell- 

 mayr (Cat. Birds Am., vol. 13, no. 10, 1937, p. 49) puts into oryzivora. 

 The forms are supposedly separable on size, but Peter's statistics are 

 not at all convincing. The break between hnpacifica of southern Mexico 

 and oryzivora is supposed to be in central Panama, but there are no 

 detectable differences in size between birds from Chiriqui, Los Santos, 

 the Canal Zone, Darien, or Colombia. A perfunctory examination of 

 birds from north of Panama disclosed no significant size variation. 

 Nor are color differences (more violaceous as against more bronzy 

 gloss in the nominate race) apparent. Until there is good supporting 

 evidence for recognizing geographic variation in this species, it should 

 be regarded as monotypic. Parkes (Condor, 1954, p. 229) has shown 

 why Scaphidura, not Psomocolax, is the correct prior name for this 

 genus. 



The Giant Cowbird, formerly known in English as the Rice Grackle, 

 is indeed sometimes found with cattle. It rides on their backs, where it 

 picks off parasites, as well as taking insects flushed by the cattle as they 

 move about. It also feeds independently in fields and pastures, on the 

 exposed banks of rivers, and in trees. One I collected when it came 

 to drink at a river in Los Santos had the throat filled with hulled rice 

 eaten in a nearby field. Except for the brief season when these birds 

 are depositing their eggs in the nests of oropendolas and colonial caci- 

 ques, Giant Cowbirds are found in flocks in which females out-number 

 males; often they feed with other icterids or with Groove-billed Anis 

 (Crotophaga sulcirostris) . Courtship occurs when the birds are in 

 flocks: the males parade with the neck ruff distended and the bill bent 

 down on the foreneck; sometimes when approaching a female, a male 

 will bob up and down while in this posture. When skinning a male I 

 found that the neck skin was loose so that it slipped readily over the 

 head, and a sheath of dermal muscle was spread broadly over the dorsal 

 and ventral sides. Presumably this is associated with the displaying of 

 the ruff. 



Female Giant Cowbirds wait patiently around the colonies of oropen- 

 dolas and caciques for the opportunity to deposit an egg in one of their 

 nests. They are often driven away, but not so vigorously that it is im- 

 possible for them to slip in and out of a nest. There are several de- 

 scriptions of the eggs. Twelve taken from a colony of Cacicus cela in 

 Suriname (Haverschmidt, Bull. Brit. Orn. Club, 87, 1967, pp. 136-137) 

 were pale blue with a few small black spots and hair lines. Eight were 

 elliptical, four oval. They measured 30.2-35.3x25.1-28.0 mm. The 



