NUTTALL'S WHITE-CROWNED SPARROW 1321 



captures of individuals surviving to their first winter comes between 

 then and the next winter season. From then on, the decline in 

 retrapped survivors is much more gradual. 



The Linsdales' study reveals wide annual variations in the ratio of 

 imma hires to adults trapped. In 5 out of 10 seasons the ratio of 

 immatures to adults was about 1 to 1. As a corollary, the average 

 percentage of immatures per year for the 10-year period from 193S-39 

 through 1947-48 was 52.6. Yet in 1943-44, the ratio was about one 

 immature to three adults, whereas the next season the ratio was re- 

 versed. This indicates the false impression that can be gained from 

 sampling of atypical years. 



The work just discussed is one of the most exhaustive banding 

 operations involving white-crowned sparrows ever carried out. Yet 

 the investigators state: 



In reviewing these observations, attention is directed to the small size of 

 the area concerned in these winter studies. A long strip of 20 acres would 

 include every trapping station as well as the ranges on the Reservation of nearly 

 all the individual birds concerned. When this is compared with the long line of 

 travel, over a thousand miles for the migrant species, the remarkable effectiveness 

 of the controls over the birds which come and stay and return repeatedly between 

 the two homes is given special emphasis. The rigidity of these controls is further 

 demonstrated when we realize how small a part of the whole population of each 

 species is represented on our minute area. If 4,000 crowned sparrows [here 

 Linsdale refers to both golden-crowned and white-crowned sparrows] have 

 wintered on our 20 acres in the last 11 years, how many have come to the 100 

 million acres of California? How was each of them able to find and stay in its 

 particular home area? Before we make guesses pertaining to these questions 

 we need to know more about what the birds really do. 



One answer to some of these questions may be forthcoming from 

 an experimental study of homing in Zonotrichia leucophrys and 

 atricapilla begun in 1961 at San Jose, Calif., by Richard Mewaldt 

 and his students. Mewaldt is attempting to find out, not what the 

 birds do under natural conditions, but what they can do under extraor- 

 dinary conditions they would not meet in nature (Mewaldt, 1962a, 

 1962b, and 1963; Roadcap, 1962). The results to date on displace- 

 ment of white-crowned sparrows are briefly summarized here. He 

 and his co-workers displaced 65 white-crowned sparrows of the races 

 pvgetensis and gambelii distances of between 9 and 164 miles from the 

 banding station at San Jose. The most significant return was made 

 from Visalia, Calif., 164 miles away, by a first-year pugetensis in only 

 7)$ days. This bird had to cross the interior coast ranges to make 

 its return. 



Experiments with releases at much greater distances from the 

 banding station are in progress. During the 1961-62 winter season, 

 Mewaldt shipped 233 Puget Sound and 79 Gambel's sparrows by 

 commercial aircraft from San Jose to Baton Rouge, La.; 67 of the 



646-737— 68— pt. 3 6 



