1914] Grinndl: Mammals and Birds of the Colorado Valley 139 



Phalaenoptilus nuttalli nuttalli (Audubon) 

 Nuttall Poor-will 



Phalaenoptilus nuttalli nitidus Brewster 

 Frosted Poor-will 



Poor-wills w-ere first noted the evening of February 28 at Mellen ; 

 then March 3, at The Needles ; thenceforth at every one of our stations 

 all the way down the river to Pilot Knob, May 12. The mellow call 

 was heard practically every night when the wind was not blowing. 

 As with the nighthawks, the poor-wills appeared to spend the day out 

 on the desei"t. One individual was flushed near Ehrenberg from the 

 stony surface of a wash in the shade of a palo verde. In the evening 

 the birds appeared at dusk in the river bottom, alighting in charac- 

 teristic fashion on spaces of bare ground or in roads, not infrequently 

 on mud bars in the river, or skimming low over the water itself. 

 Their proneness to alight on the wet mud at the edge of the water 

 was evidenced by the packed balls of mud firmly dried on the toes of 

 several of the birds shot. In the evening of April 19, eight miles east 

 of Picacho, fully a dozen poor-wills were observed. There was a lot 

 of broken-down fencing close to the river near our camp at this point ; 

 the birds congregated here as a basis for foraging and consociating, 

 resting on the posts as well as on the prostrate poles, evidently in 

 preference to alighting on the sticky mud of an overflow depression 

 on the one hand or the river margin on the other. 



The series of eighteen specimens of this bird secured at once aroused 

 inquiry because of the large range displayed in size and pattern of 

 coloration. Even in the field, as the specimens were collected, con- 

 spicuous differences were noted and the suspicion aroused that really 

 two subspecies were represented, one being the resident breeding form, 

 the other a winter visitant. The first clue to discrimination came 

 through observing the state of activity of the reproductive organs. 

 Of two birds shot the same evening at Riverside Mountain, one, no. 

 12780. with testes small, was relatively large, dark, and coarsely 

 marked ; the other, no. 12781, with testes very large, was small in gen- 

 eral size, narrow-barred, and notably pale. In five other birds, field 

 examination showed the same relative state of affairs (see accompany- 

 ing tables). It is of course regrettable that state of reproductive 

 activity was not recorded of all the poor-wills taken. 



The seven birds, dissected in the field by the writer, would seem 

 to provide adequate basis for the conclusion that two races were repre- 



