GAMBEL'S WHITE-CROWNED SPARROW 1335 



sparrows, the similarity of calendar dates for original capture and 

 return seemed to occur too frequently to be purely coincidental." 

 Of 121 banded GambeFs sparrows recaptured by Crawford in suc- 

 ceeding years, 50 percent were taken within 30 days of calendar date 

 of original capture. 



The waves of migrants arriving at a given place on the wintering 

 grounds do not stop with the onset of winter. Elliott McClure 

 (personal communication), who banded nearly 3,000 white-crowned 

 sparrows (presumably all or nearly all gambelii) at Bakersfield during 

 four winters, stales: "A wave of birds appeared to enter the area in 

 October, increase in November, and decrease in December. This 

 was followed by another increased flow through January and February 

 which then decreased in March and April." After presenting several 

 possible explanations for the wave-like movements of white-crowned 

 sparrows suggested by the banding records, McClure concludes, 

 "The wave action of these birds seems inescapable, both going south 

 and returning north, and the mass of birds moving was great enough 

 that unmarked ones were constantly entering the vicinity of the traps. 

 Jean M. Linsdale (1949), working with White-crowns at Hastings 

 Reservation about 150 miles north of Bakersfield and in the coastal 

 range, found a similar wave action but with different distribution 

 during the winter months." Although, as Mewaldt's data discussed 

 in the following paragraph indicate, one cannot assume that the 

 mid-winter waves observed by McClure came from any particular 

 compass direction, the interesting point is that influxes of birds 

 appeared during months when migration proper does not occur. 



That white-crowned sparrows are potentially mobile in winter 

 is indicated by the trapping records of L. R. Mewaldt (1963) who 

 trapped and banded white-crowned sparrows (Z. I. pugetensis and 

 Z. I. gambelii) at San Jose, Calif., for 8 consecutive seasons. From 

 1954-55 through 1960-01, the total numbers of both races trapped 

 ranged from 181 to 292 per season, or an average of 227.1 for these 7 

 seasons. In 1961-1962 Mewaldt removed large numbers of banded 

 white-crowns and shipped them by air to Baton Rouge, La. One 

 of the many interesting results of this work was the increase in numbers 

 of white-crowns trapped at San Jose that season — a total of 670 un- 

 handed individuals. Mewaldt (1962) removed 430 birds for his 

 homing experiment. He states: "Repeated removal of the 'hard core' 

 of dominant birds coming to bait at the banding station probably 

 permitted population pressure to fill the vacuum thus created." 

 While the situation created by removal of many wintering white- 

 crowns is obviously an unnatural one, the fact that so many birds 

 came to Mewaldt's station shows the inherent mobility of win- 

 ter flocks, and also that no assumption can be made as to the 



