The Detritus-Based Trophic System 453 



energy must be expended for thermoregulation throughout the season, 

 and particularly in early June. Various energy-demanding processes and 

 activities — territorial defense and display, egg formation, incubation, 

 care and brooding of chicks, molt (in dunlin and longspurs), and pre- 

 migratory fat deposition — are distributed through the season. This led 

 Norton (1974) to suggest that the daily energy requirement for mainten- 

 ance plus productive activities remains near the maximum metabolic rate 

 throughout the period of residence on the tundra. 



Differences among species in the energy requirement for reproduc- 

 tion stem primarily from differences in body size and in duration of resi- 

 dence on the tundra (Table 11-12). Energy required per nesting attempt 

 (Figure 11-11) is greatest in pectoral sandpipers and dunlin, and least in 

 semipalmated sandpipers; however, when differences in nesting density 

 are included to estimate total energy removed from the tundra (Table 



Chironomid 



P hannai 



T. carinifrons 



10' 



IQl 



c 

 E 



E 



V 



o 



c 



o 



a: 



a. 

 o 

 o 



^ 10° 



Q. 

 w 

 m 



or 



10 



I MUM 







_L 



I 



I 



10^ 10' 



Prey Size, mg d.w. 



10' 



FIGURE 11-11. The requisite rate of prey capture (items 

 per minute of foraging) to satisfy daily energy require- 

 ments for birds with different energy requirements and 

 different proportions of the day available for foraging. 



