396 



BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



[T0I.V. 



ICTEEIDvE. 



56. MoLOTHRUS ATER (Boclcl.) Gr. — Coiobird. 



Winters in numbers on tlie Eio Grande, but by the first of May is 

 replaced by the dwarf variety. 



57. MoLOTHRUS ATER OBSCURUS (Gm.) Coues. — Dwarf Cowhird. 



This Cowbird, distinguishable from the Northern form in little else 

 but size, arrives in Texas from Mexico in April, and throughout that 

 month is associated with all species of Blackbirds and the other Cow- 

 birds, about cattle-pens, barn-yards, and corn-cribs. This and the 

 Bronzed or Eed-eyed are the only ones that remain at Lomita to breed. 

 Its habits are similar to its well-known relative of the North. By the 

 middle of May it commences to lay. Of six eggs before me, three were 

 taken from nests of Hooded Oriole, one from the nest of Bullock's Oriole, 

 one from the nest of the Texan Orchard Oriole, and one from the nest of 

 the Green Finch. In one of the nests of Hooded Oriole was also an egg 

 of the Red-eyed Cowbird {Molothrus ceneus). 



I observe that this Cowbird selects the homes of birds fully as large 

 as itself, and also that the eggs of the intruder do not often exceed in 

 size those with which they are deposited. It would be interesting to 

 know, under such circumstances, which are hatched first. So very few 

 Warblers and other small birds breed on the Lower Eio Grande in pro- 

 jportion to larger ones that it maj^ be less trouble for the Cowbirds to 

 make use of the larger nests. The eggs of this Cowbird vary in length 

 from .80 to .70, averaging a little under .78. In breadth they are very 

 constant, averaging .60. 



5'8. MoLOTHRUS JENEUS (Wagl.) Cab. — Bronzed or Eed-eyed Cowbird.* 



More abundant at Lomita than at Hidalgo the previous year. I can 

 add little to the account of the breeding habits of this recent addition 

 to our fauna beyond what Dr. Merrill has so fully given in the Bulletin 

 of the Mittall Club (ii, No. 4, x). 85) and in his recent pamphlet (Notes 

 on the Orn. of Southern Texas from February, 1876, to June, 1878, Proc. 

 Nat. Mus.). I found but three of its eggs, as I left the Eio Grande 

 in the last of May, when the birds had just begun to lay. Two of them 

 were laid in nests of Hooded Oriole, and one in that of the Blue Gros- 

 beak. One nest of the Hooded Oriole contained also one egg of the 

 Dwarf Cowbird, with but one egg of the rightful owner. The first egg 

 was taken May 24. The color of the egg of this species is the faintest 

 bluish-green, similar to that of the Blue Grosbeak, and as fugitive when 

 * For full descriptions of this bird see Bull. Geol. and Geogr. Surv., vol. iv, No. 1, p. 23. 



