1914] Grinnell : Mammals and Birds of tht Colorado Valley 203 



being very broad, tending to cover in some cases the whole pileum, 

 though becoming concealed beneath an olive wash posteriorly, and 

 with a mixture of yellow. 



Extreme examples of scirpicola are conspicuously different from 

 the nearest approach to it in appearance among many specimens of 

 occidentaUs from Nevada, northern California, British Columbia and 

 southeastern Alaska. But among the considerable number of speci- 

 mens from the range of scirpicola, there are some which have so far 

 defied every effort to distinguish them satisfactorily from occidentaUs. 

 The problem is complicated by the fact that there are yellowthroats 

 moving through the range of scirpicola at the same season that the 

 resident birds are nesting, that is, until the last week in April at least. 



The twelve Colorado Valley examples referred to scirpicola (char- 

 acterized by Grinnell, 1901, p. 65) are listed in an accompanying table 

 to show locality and date of capture, and measurements. One speci- 

 men, no. 13723, deserves special comment because of an extraordinary 

 aberrancy in coloration : the whole throat is clear, intense cadmium 

 yellow, in marked contrast with the normal canary yellow of the chest 

 and remaining lower parts; otherwise the bird is like the average. 

 This extra intensification towards orange, though over a restricted area, 

 is probably a color change of significance along the same line as dis- 

 cussed in this paper under Colaptes chrysoides. 



The tule yellowthroat was closely restricted to dense vegetation 

 growing close beside or over water. Tules bordering sloughs formed 



MEASUREMENTS IN MILLIMETERS OF GEOTHLYPIS TE1CHAS SCISPICOLA 

 FROM THE COLORADO VALLEY 



Mus. No. Sex Locality Date Wing Tail Tarsus Culmen 



Riverside Mt., Calif, side 

 Riverside Mt., Calif, side 

 Ehrenberg, Ariz, side 

 5 mi. N. Laguna, Ariz, side 



4 mi. S Potholes, Calif, side 



5 mi. N.E. Yuma, Calif, side 

 5 mi. N.E. Yuma, Calif, side 

 5 mi. N.E. Yuma, Calif, side 

 Near Pilot Knob, Calif, side 

 Near Pilot Knob, Calif, side 



Average of the males, 



Opposite Cibola, Calif, side 

 4 mi. S. Potholes, Calif, side 



