914 U.S. NATIONAL MUSEUM BULLETIN 23 7 paet 2 



prebasic (postnuptial) molts occur mainly from mid-September into 

 October; they are notable for the apparently aimless, disorganized 

 order of the tail feather molting. Females seemingly lag behind 

 males in all molts. (Molt of juvenal feathers in birds in spring is 

 unusual, according to Humphrey and Parkes, 1959.) 



Molt between November and May seems to be a most exceptional 

 event in Arizona. I have seen but one molting specimen — the male 

 of a pair taken in swale habitat by J. A. Munro on Jan. 31, 1952. It 

 was molting on the throat and on the middle (median) part of the 

 breast and especially of the belly. 



Farther south in Sonora, a smaller race was still in worn alternate 

 plumage at the end of October 1946, with the males only just starting 

 the prebasic molt (Pitelka, 1951). Nesting here is apparently later 

 than in Arizona. If K. T. Moore (1946) is correct in saying that 

 "some July and August birds are in the midst of molt," the prealter- 

 nate molt must often be correspondingly late in Sinaloa. But Moore's 

 statement that the species molts at any time of year in the Tropical 

 Zone is not supported by the material I have examined. Nor can I 

 believe that "many March individuals have completed their pre- 

 nuptial [=prealternate] molt" there, as Moore states. 



Just as the timing of the prebasic (postnuptial) molt is evidently 

 affected by the timing of the nesting period, so also is the extent, 

 timing, or perhaps even the very occurrence of the prealtemate 

 (prenuptial) molt. In years of unusually early nestings in Arizona, 

 the latter is often curtailed or postponed until after the young leave 

 the nest. I know of no clearer illustration of the undesirability of 

 tying the names of plumages and molts to the breeding cycle in the 

 classic Dwightian tradition. 



Particularly instructive is a smaU family group taken on June 12, 

 1958, in swale habitat. The young one, a female, was fuUy grown, 

 with the tail 65.2 millimeters and not sheathed at base; she was well 

 into the first prebasic (postjuvenal) molt. The parents were both 

 adults more than a year old. Except for one of the outer, longer 

 tertials in each wing, the prenuptial molt of the father had been 

 postponed and was just starting, chiefly on the back but also on the 

 breast and belly. The mother, on the other hand, had molted nor- 

 mally, or nearly so, even while incubating, and was now well into the 

 prealtemate or prenuptial molt. Her oviduct was now small, and 

 the brood patch no longer vascular; her largest ova were 1.5 and 1.8 

 millimeter in diameter. That the molt is a prenuptial one seems 

 certain. The primaries and secondaries show no molt, though that 

 of the tertials is near completion, and the only short rectrices are the 

 central pair, now 34.5 and 44.6 millimeters long. One outer rectrix 

 is missing, and the other appears fresh. All other tail feathers are 



