BIOLOGICAL ASPECTS 



323 



ing weight during the early season. One well known migratory sand- 

 piper, Erolia melanotos^ showed an increase in weight during the 

 early season. There is wide variation in the weight of individuals of 

 this species (see p. 197) . 



In three species {Turdus 7nigratorius migratorivs, Oenanthe oenaiv- 

 the oenanthe, and Motacilla -fiava tschutschensis) the weights were 

 not distributed in a manner that would show seasonal change. The 

 weights of two species of Turdidae were affected by the heaviness of a 

 few individuals just before migration southward and by sparse early 

 season observations. The weights of Motacilla are too few to indicate 

 a trend. 



Less extensive data is available to show the condition of female 

 birds. In 5 species (Pluvialis dominica dominica, Heteroscelus in- 

 canum, Erolia iairdii, E. minutilla and Galcarius lapponicus alas- 

 censis) weights declined in the early season by between 10 and 15 

 percent. In the early part of the season the females of Lohipes 

 lohatus gained weight. The females of Acanthis homemanni exilipes, 

 like the males, showed no change. Because of my belief that they are 

 not long-distance migrants they are not comparable with the other 

 birds. The number of weights of females of Zonotrichia leucophrys 

 gambelii is too small to show a trend, but it is reported for its relation 

 to Mrs. Oakeson's interesting studies of this race. 



Although the records of fatness are fewer than those of weight 

 and not numerical, they show a general correspondence with the pre- 

 dominating decline in weight after the first birds arrived. The males 

 of 13 species and the females of 2 species which declined in weight 

 during the early season also diminished in fatness. The males and 

 females of Acanthis did not show a significant change in fatness or 

 in weight. In comparison with many other species they were not 

 fat. Males of Erolia melanotos appeared to gain in fatness as they 

 did in weight. The species Turdus, Oenanthe, and Motacilla gave as 

 uncertain indications about fatness as they did in their weight. 



These data are summarized in table 16. 



Table 16. — Summary of differences in weight and fatness of common migratory 

 species after arrival at Anaktuvuk 





Weight 



Fatness 



Type of migrant 

















Lost 



No 



Gained 



Lost 



No 



Gained 







change 







change 





Long migration 















Males 



13 



1 



1 



14 







1 



Females 



5 







1 



2 







1 



Short migration 















Males 





2 







2 





Females 





1 







1 





