• CASSIN'S KINGBIRD. 251 



could only he reached by placing- a pole agaiust the limb and climbing to it. 

 They are lully as demonstrative as the Arkansas Kingbird when their nests are 

 disturbed, and are equally courageous in the defense of their eggs and young. 

 The nests are large, bulky structures, larger than those of tlie preceding species, 

 but composed of similar materials. An average nest measures 8 inches in outer 

 diameter by 3 inches in depth. The inner cup is 3^ inches wide by If deep. 

 Sometimes they are pretty well concealed to view from below, but they can 

 usually l)e readily seen at a distance. 



From two to five eggs are laid to a set. Sets of three or fdur are most 

 frequently found, while sets of two and five are rare, but I have found botli, 

 incubation having already commenced in the smaller set. This lasts from twelve 

 to fourteen days, and is almost always, if not exclusively, performed by the 

 female. I have never noticed the male on the nest. The eggs are similar in 

 color and markings to those of the Kingbird and Arkansas Kingbird, and about 

 the same size as the latter, but on the whole they are not quite as heavily spotted. 



The average measurement of forty-four eggs in the United States National 

 Museum collection is 23.62 by 17.47 millimetres, or about 0.93 by U.69 inch. 

 The largest egg of the series measures 27.94 by 19.30 millimetres, or 1.10 by 

 0.76 inches; the smallest 22.61 l)y 16.26 millimetres, or 0.89 by 0.64 inch. 



The ty])e specimen. No. 20413 (PI. 1, Fig. 18), from the Bendire collection, 

 was taken by the writer on Rillito Creek, Ari7X)na, on July 15, 1872, and is a 

 rather large-sized egg, while No. 26146 (PI. 1, Fig. 19) was collected l)y Dr. 

 Edgar A. Mearns, United States Army, on the east side of the San Luis Moun- 

 tains, New Mexico, on June 17, 1892. The two specimens represent about 

 average-marked eggs of this species. 



92. Pitangus derbianus (Kattp). 



DEEBY FLYCATCHER. 



8aurophaf/us derbianus Kaup, Proceedings Zoological Society, 1851, 41, PI. XXXYI. 

 Pitangus derbianus Sclater, Proceedings Zoological Society, 1856, 297. 



(B _, C — , R 308, 3(31, U 419.) 



Geographical range: North to tbe lower Rio Grande Valley in Texas; south 

 through Mexico and Central America to Colombia, Venezuela, and Trinidad, South 

 America. 



The Derby Flycatcher, also locally known as the "Bull-headed Flycatcher," 

 "Mexican Pitangus," and "Rio Grande Flycatcher," can only be considered as 

 a rather uncommon, summer visitor in the lower Rio Grande Vallev, in southern 

 Texas, whei-e it breeds in very limited nund)ers, thougli in the adjoining States 

 of Tamaulipas and Nuevo Leon, in eastern Mexico, it appears to. be fairly 

 common, and it is equally so throughout the greater portion of tlie Mexican 

 Republic, both in liot and temperate zones, where it sometimes reaches an 

 altitude of .5,000 feet. It also breeds throughout Central America in suitable 

 localities. 



