mens from the Pampas, and which is the only color present in the
specimens identified by Dr. M. Instead, it is marked all over its surface
with handsome spots and blotches of a deep reddish-buff, almost
cinnamon in shade, completely obscuring the ground. Excepting in
size, it most resembles an egg of Hierofalco islandieus. — T. M. B.
138. Falco columbarius, Linn.
Not uncommon during wiuter. — (Dresser, Ibis, 1865,323.— Sennett, B. Eio Grande, 42.)
139. Falco sparverius, Linn.
Abundant from about the middle of September until the early part of April. All the specimens obtained were var. sparverius. — (Sennett, B. Eio Grande, 4:2.—Tinnunculus s., Dresser, Ibis, 1865, 323.)
140. *Polyborus cheriway, (Jacq.)
A common resident, but more abundant in winter than in summer. This seems to be due to a partial migration, from the north, of birds in immature plumage, for the number of mature individuals does not seem to vary. I do not think that the perfect plumage is acquired for at least two years. I have but little to add to the many accounts already given of this bird, except to say that, at times at least, it is more active than some of the descriptions would lead one to infer. I have seen a Caracara chase a jackass-rabbit for some distance through open mesquite chapar- ral, and while they were in sight the bird kept within a few feet of the animal and constantly gained on it, in spite of its sharp turns and bounds. If one bird has caught a snake or field-mouse, its companions that may happen to see it at once pursue, and a chase follows very different from what is seen among true Vultures. The nests are bulky platforms of small branches, with a slight depression lined with fine twigs, roots, and grasses, or sometimes altogether without lining : they are placed in trees or on the tops of bushes, at no great height from the ground. Both sexes incubate. I have not found more than two eggs in one nest, and these are laid at an interval of three or four days. Eleven eggs average 2.28 by 1.84. The ground-color is a deep chocolate or red- dish-brown, more or less thickly covered with several darker shades of the same. — (P. tharus, Dresser, Ibis, 1865, 329. — P. tharus auduboni, Sennett, B. Rio Grande, 42.)
141. Elanoides forficatus, (Linn.)
This beautiful bird I have observed on but few occasions, and do not tftink that it breeds in this immediate vicinity. Nothing can be more graceful than its movements when pursuing insects, and for such a large bird it is very active. — (Sennett, B. Eio Grande, 42. — Nauclerus fur- catus, Dresser, Ibis, 1865, 325.)
142. Elanus leucurus, (Vieill.)
Seen on a few occasions, but is rare,
